Hmmm... I don't really like the idea of purposely dirtying my guitar or consciously allowing my guitar to get dirty.

I think some dirt/nicks/bruises give a guitar character. I feel it gives the guitar character. It's like how people pay hundreds of $$ for a Jaco bass that's been faithfully and authentically distressed.

Basically, I don't clean my guitar every single time I play, but I don't play with dirty fingers or let it fall around everywhere.