A seemingly little-known fact is that different guitars produce different sounds. Seriously, its not just aesthetics (OK, it is a lot of aesthetics, but that's not all). Plenty of people prefer the sort of pointy ones, whereas some like classic curves, and that can be just as valid a decision: you probably wont see a heavy metaller with a Daisy Rock guitar. Or anyone, to be honest, because a butterfly-shaped guitar isnt all that appealing. Sometimes if youre playing a gig, youve got a song where you need a heavier, crunchier sound. The nice telecaster you just used isnt going to be able to service that bite as much as a bold SG, so a change of guitar is necessary. Its like telling a drummer that all they can use is the snare drum. And its a great excuse to spend every last penny on beautiful guitar after beautiful guitar.