I've resisted from posting and getting dragged into this poorly worded question (how can you prove what isn't?)
Not speaking about the four major music labels, but there appear to be some misconceptions about the role of record labels among many /. readers, who may have had little or no direct interaction and dealings with indie labels, which needless to say have historically been responsible for breaking out a lot of very innovative talent. Besides the old distribution and manufacturing duties, the primary functions of such a label are to help with the artist's image, promotion, publicity, airplay, guide their career with a choice of songs, producer, and many other things that most professional musicians do not have time, resources or the inclination to be doing when they are busy making music and performing it. Cue in the obligatory contrarian "I did it all myself" to negate this statement, but most successful creative people would prefer focusing on what they are good at instead of dealing with merchandising, filling out aggregator licensing agreements or dealing with graphic artists. That there are a few who are an exception to this doesn't make it any different for the majority of music professionals out there, whether artists, composers, etc... who really WANT someone by their side to partner with them in making their release a successful one, rather than merely just adding yet another entry into the dustbins of recorded music.
But on the artistic side of things, there is no question that today, many artists are not able to spend the time necessary for crafting songs with the same kind of quality and loving care they once did. Again, those who think that having a copy of Garage Band or Cubase along with two microphones and a cheap Mackie board at home is enough to make fantastic music are in my opinion mostly deluded on thinking that they can come close or even beat teams of well-honed and dedicated professionals at the top of their craft, whether those be recording engineers, assistants, drum techs, roadies, as well as arrangers (who even remembers those?), or the dedicated studios and the maintenance technicians that provided the environment needed to comfortably record one-of-a-kind performance without any technical glitches, and so on.
What has happened is that the entire ecology that supported record-making has imploded, and while a few of those at the top of their trade still find work elsewhere or for wealthy artists, most of the people that were associated with recording studios and making music professionally have moved on to other related activities like audio for broadcasting, gaming, advertising or movies. The budgets just aren't there for the most part anymore, to put together full-fledged recording sessions with great professional players.
Yes, as many like to immediately point out it is possible to do most of this stuff very inexpensively on one's laptop... yet having access to the gear does not ensure that those who operate it have a modicum of taste, experience and knowledge to turn these simple tools into something that will make tantalizing, mind-blowing recordings, and that they will have the expertise to coax that special magically inspired performance out of an artist, and so on. Of course, it is possible to do everything by yourself, but the chances of the results of this being on the same level as Stevie Wonder and Prince are so infinitesimally small that one could easily wonder why it should even be mentioned at all, except as a straw man argument.
To deny the combined expertise, know-how and vast irreplaceable contributions to record-making that all of these side helpers have traditionally brought to the table has recently been a popular point of view harbored by those who feel they know better, which they are welcome to in a sense, because the sheer mediocrity, overall uninspired and depressingly bland results of such one-man-band recording sessions are right now cluttering more people's in-boxes that one could shake an army of sticks at, to little or no visible effect at all.
When it comes to recorded music at least, there has been very clear and observable impact of the consequences of most people refusing to pay for albums and singles. Radiohead and all other major bands aside (as they've obviously benefitted from years of being supported by a major's promotion machine until they reached that 'critical mass' in popular culture, becoming arena-size touring bands that don't need any more publicity, yet they certainly did not accomplish that on their own) it has resulted in a big majority of the significant helpers and contributors in many key areas to just leave the field and find other activities. This is not something that is immediately measurable, but over time it will have a significant impact on the quality of what albums and singles get out there, as little by little some of those contributions will for the most part not be replaced with something equivalent, just a cheaper ersatz if any at all.
While I do not expect this comment to be popular, I think that it should at least be considered, even if the readers do not agree with what it says. From someone who has spent a lifetime in the business of recorded music, take my word that this will not ever revert back to what it once was, because of many of those professionals leaving the field and a majority of the facilities where this was recorded having closed down altogether. Recently was surprised to hear something along those lines when speaking with some teenagers who were decrying how bad a lot of new music is and sounds when compared to older stuff from the 70's and 80's. I was a bit taken aback, but they seemed to clearly be aware that something was missing. That unquantifiable 'something' might prove very elusive indeed to ever track down in this age of 'everything free', where a great majority of people appear to be in denial, looking as if suffering from the results of a temporary hypnotic ailment that makes them believe that technology can replace creativity and expert knowledge.... of course genius will always occasionally find its way to sift through all of these impediments no matter what the material circumstances, but it is a bit sad that some much accumulated expertise and knowledge is being laid to waste, and that more people aren't consciously aware that this has - in my opinion - directly impacted the quality and possible timelessness of the recorded works being produced.