The one complicating factor, though, is that discrete sound cards are being squeeze from both sides: With even integrated GPUs offering HDMI and displayport audio, and even all but the most spartan (usually super-cheap and/or strictly business oriented) onboard audio supporting S/PDIF, the option of an external DAC or receiver becomes much more attractive, especially if you already have one that you like or want to be able to use other audio sources with a relatively expensive piece of high quality audio gear.
The performance of the analog components of onboard audio is, indeed, going to be more 'endurable' than 'good'; but digital logic is crazy cheap and (mostly) either works or doesn't, and basic boring onboard audio often has less ghastly driver mess than the cards trying to 'value add'(Creative, specifically, being a ghastly offender).
It's not as though they are a ghastly scam or anything, if you want to be able to plug a nice pair of headphones straight into your PC rather than an outboard module that's totally understandable; but they do occupy a slightly precarious middle ground between mostly-competent onboard audio and the full array of audio gear that accepts digital input.