I was talking to a brilliant engineer friend the other day who mentioned they never get to build anything from the ground up. Their entire career has consisted of maintaining other people's (often quite poor) code.
In a perfect world, we'd all get to write code from scratch, it would work perfectly, and we would put it into a bin in the sky, never to be looked at by anyone again.
We all know that's not how it works. Code need to be maintained.