Under the shower, your brain switches to a bit of an alpha state, the same when you go to sleep and you start using your right brain more, so you find solutions to problems intuitively rather than rationally (which means you aggregate and summarize all of your rational knowledge, without even knowing about it).

It's good to train your right brain even if you do a lot of programming (which is totally a left brain activity), it will help you to be a better in that either!

Oh yeah, I'm aware of that.

I'm just making the point that a lot of programmers are thinking of code when they're not directly working on it. It's the nature of what we do.