I think this is something that is wrong that is being percieved by most users:

People are looking at communities as a way to segment reward.

But this shouldn't be the reason of communities existing.

Communities should be about segmenting topics, not rewards.

Communities should be about finding content that is relevant to your own interest.

So, since i am really into trading and investing, and have been learning about it for the past 3-4 years, i wanted to have a place to people share and talk specifically about this topic, and not have posts spread over all other communites where everyone talk about everything.

And with the crosspost implemented by @steempeak this make things even more interesting, because everyone can post on their "generalist" communities, but crosspost it on each "specific" community, kind of creating a repository of specific information.