You have the satisfaction to say that YOU made it yourself, and you are not using someone else's work. Have you ever modified a car? or modified your desktop/Windows appearance? painted your room?
It's the same thing, you can just say "Hey, i did that". And - i speak for myself here - it was a more a challenge than anything else. I was used to winamp when i decided to code my first mp3 player, and it had a lot of the features Winamp has, and some that it didn't have. You just make it the way YOU want, not the way a bunch of coders you never heard of wanted.
