Not 100%. Often, when it comes to recording a file to tape over the radio, unless you've been doing it for a while, and are very proficient in it, you tend to loose some quality in the song. I remember doing this, and had that problem.
In the case of MP3s, these tend to be directly ripped from a CD, so the quailty usually doesn't suffer as much, though it is possible. MP3s are also compressed, meaning that that take up less space than the normal .wav versions of said files.
However, what most people take advantage of is the right to back up your material. This is often used for video games, in that you can have a copy of the game, in order to back up your exisiting game, in case it is corrupt. Similar claims are used for music, which I tend to favor.