There are reasons why this bitrate and sampling frequency are used and it can be heard. It is not futile and it is not just big numbers for the sake of it. I speak as a technical director for an AV company and as man who built several home and project studios and was part of 3 major studios migration from analog to digital technologies. I once was a teacher and technical supervisor in a sound design school.
-you can and you WILL hear the difference with 16bits. It basically record finer amplitude variations than 16bits, therefore the dynamic range is increased and there is less approximation of values when the sound is digitized. the end result is that stereo spacialization is usually better as the right and left channel amplitude differences are closer to reality and very fine variation will lead to audible different result. Less quatization noise is heard (the low amplitude pop corn noise and "8bit feel" you get when listening to low amplitude digital recording) as lower amplitude values are represented with more bits and therefore are less coarse. More importantly any processing playing with amplitude is rendered much more accurately with finer detail. A digital compressor/limiter won't screw you stereo image, an expander won't bring more distortion to your mix by amplifying quantization noize for example. Echos and especially reverb will be MUCH finer and accurate, the tails won't cut off and won't sound like white noise.
- this one is tricky as it has a lot of use in the studio but it can barely be heard even on the best systems. Basically pretty much all AD/DA system uses brickwall filters to filter frequencies above 20KHz, the limit of a very healthy ear, so as to prevent foldback frequencies. The higher the sampling frequency the softer the slope of that filter is because the foldback won't happen until 96KHz is reached compared to 22KHz on 44.1KHz. the brickwall filter at 44.1KHz is harsh and many people with good sound system were complaining (me included) that it could be heard and was annoying. At 192KHz it is softer, enough to not be a disturbance. On the other hand the most important reason and use for 192KHz is latency. When recording someone in the digital world you have to deal with the fact that as a certain number of samples will have to be created before what goes in, goes out, at 44.1KHz there was an audible, annoying delay, if audio was processed it was unlivable for most musician. at 192KHz this delay is essentially eliminated and only the most discerning musician will be annoyed by it. So in that sense 192KHz is not really needed for most people and indeed very few people have systems that will indeed let them hear the difference with 44.1KHz but it is there.
I guess we all like to believe there is a big evil industry in all domain that make us buy stuff we don't need, I like to believe my i5 750 is as good a an i7 960 for what I do but the reality is the i7 960 IS better and with the right application the difference means a lot. Same goes for cars, a 2001 Toyota echo will get me around but a more expensive cars will get me around in more comfort will less issues. Same goes for audio, most people using gaming headphone or 5.1 gaming audio setup and cheap all-in-one sound system will never ever hear the difference between 16bit 44.1KHz and 24bit 192KHz but it doesn't mean it is not there and it doesn't mean it is not significant and that it's a lie. It might not be a necessity but for professionals like me (as in "it is how a make a living" not as in "I am an expert, listen to me") it is significant. For audiophile it is significant also and for people who listen to music all day (ear fatigue will come in much later with 24bit 192KHz than with 16bits 44.1KHz).