Just my opinions.
About sound quality.
MP3's come in different 'kbps'. From very low quality (32) up to 'best quality' (320). No matter what quality you get, it's still a compressed version of the original CD file. A song on CD for instance will take up at least 50MB of space. Where the same song in the best MP3 quality would take up about 10MB. So regardless of whether you can personally hear it or not, there is always going to be a quality loss. Most people playing music through iPods or cheap stereo systems probably won't notice. But put the music through something like a Luxman system with Polk Audio speakers and MP3's sound awful compared to the CD's every time.
Most of the online stores are selling MP3's at either 192 kbps, or 256 kbps.
The free sites are usually streaming MP3's at anything from 56kbps and up.
So... if you say you can't tell the difference, that's fine... either you don't have good enough quality equipment or your ears are not developed enough to tell the difference. But anybody who's spent years listening to audiophile quality LP's and CD's can instantly tell when it's an MP3.
About file stealing.
Every time you illegally download a song, you're affecting the quality of music in coming years. (hard concept to get your head around but hey...)
No matter what argument you want to put forward about record companies ripping people off etc etc... the end result is, the less money the industry makes from selling music, the less money they have to put back into it in the future.
So instead of bands who would take years to record a detailed album of amazing sonic quality, you'll get younger bands with inexperienced players making CD's as fast as possible in the studio so that the record company can save money.
The less the industry makes, the worse the end result will be.
As the industry continues to lose money in future, the less likely they are to sign new talent or take a chance on new bands.
It's also less likely that they'll take a chance on something new.
They'll stick with the formula that works... generic tunes that are A.M. radio friendly.