You don't even have to merge stuff from a human. I've been contributing a bluetooth driver to a certain embedded project which I use. I put a lot of work into it. The fellas have not merged it yet -- they have limited attention and for whatever reason their priorities and mine are not aligned at this moment.

Would I like it to be merged? Sure would, it would stroke my ego, and I would not have to deal with any merge conflicts with whatever else they're cooking up. Does that mean they must merge it? Sure doesn't. They didn't make me any promises. For the time being, I can just use my fork.