I'm a developer and entrepreneur, running a WordPress business right now, used to own a Drupal shop ages ago, the little I've contributed here was developed for that; later shared here and the module gained popularity thanks to theme developers adapting it.
I've learned quite a lot here, things that I could have never learned otherwise. I'm very much grateful being still part of the Drupal community.
If you are wondering whether you should contribute or not, the answer is yes definitely you should; and not just Drupal, to any open source project; every developer should contribute to at least one open source project. It's a great & unique learning opportunity at very least, and in case of Drupal it's one of the most exciting ones too, given they always go for the latest technologies and adapt them well before other platforms such as WordPress.
Thanks Drupal!