I monetized immediately upon hitting the 10k threshold. Lots of people say they won't watch a video from a small channel that has ads. Why? Anyone that uses YouTube regularly is used to sitting through ads, anyway. Doesn't bother me a bit.
Also, while making money might not be a creator's motivation, it sure as hell is YouTube's motivation! They're a business. They NEED to run ads. All things being completely equal, if there were two channels of equal status (subs, views, retention rate, etc) in the same genre, and one was monetized and one was not, which do you think YouTube has the motivation to put in front of viewer's eyeballs? The one they CAN'T make money on, or the one they CAN?
Think about that.