Wekan at GitHub currently has about 1700 public forks. There is unknown number of private forks.
At Wekan GitHub issues I see that many have developed features that they use internally in their company. The same extra features usually get implemented in every company that uses Wekan, like different ways to authenticate, etc. I still see discussions that could someone add some feature directly to Wekan, or should they make custom fork of Wekan.
When someone has custom fork, it does not get bugfixes, new features, new translations, and new platforms. Original code to some feature can be lost with some broken harddrive. Companies get shut down or merged. New companies implement same features again and again. You need to continually merge your features to newest Wekan.
When you contribute your feature to upsteam Wekan devel branch as pull request, we help to improve code quality, make the feature better, fix bugs, and add translations to multiple languages. You are improving Wekan for everyone, and you get thanked in changelog and by countless numbers of Wekan users.
On behalf of Wekan Team