It sounds like Rivers Cuomo, Weezer's lead singer, spent much of his teenage years in the garage. He could have been a bit self-conscious about performing his music in public, and he describes his garage as a safe place where he keeps some of his belongings: "I've got posters on the wall, my favorite rock group Kiss." His garage was probably a place where he could get away from it all and just write, play music, or just ponder life. It could be that Rivers didn't think Weezer would become this big, that maybe they would just be a regular garage band.
Dave - Philadelphia, PA