I would say the @needleworkmonday community works well. There is a vision and posting guidelines, and members post under the tag on Mondays. Whenever there has been any kind of process to elicit the views of the members who post, it is clear the community is significant for them, and support friendships are forming outside posting under the tag - support for illness, adversity and bereavement.
I have done some work previously looking at the growth of the accounts posting under the #needleworkmonday tag - it was about 13% over three months. That post prompted delegations from @taskmaster4450 to the smallest accounts to help them grow.
I would say that rewards (in terms of sp etc) are not critical to that community; having a place to express yourself and be acknowledged, to learn and be inspired is. Some members have gone through a transformational change as a consequence of their involvement, leading to major life changes.