I enter local contests...1) it is a way to get new work in front of like-minded people, 2) it supports the art organization, 3) it forces one to take that new image and finish it, frame it and all that, 3) the occasional award (especially cash) is nice -- more film!
I enter one annual non-local competition (Yosemite Renaissance, a multi media show/competition) as a challenge to produce an exceptional piece every year of Yosemite. Also if I get something accepted, then I have a good excuse to go to Yosemite in February for the opening (at which time I try to take a photograph for the next year's competition.) I did not get an image in last year, but something happen that was as good - a fellow I started on carbon printing did get a carbon print in the show. That was very rewarding.