Because if and when you decide to use it, it takes time generate.
Don't assume that because you feel one way today that you're going to feel the same way in five years.
I'm sure I have something
in the credit record- never missed a payment on anything since I canceled my last CC, and that was over 8 years ago.
I just can't see myself starting to use credit cards, which I hate, on the off chance that I might want to do something totally different (buy a house or whatever) later on. Not worth it.
Part of the penalty I pay for not buying into the system of credit is reduced ability to utilize that system later on - I realize and accept this. I don't really see it as a downside though, all it is going to do is keep me from purchasing things that I can't afford...