Often, well, not often, but once and a while I get a forum group join offer for a group I'm not aware of existing... And most of the time I reject because I don't like to be members of many unknown groups, except groups like customwear wearable cwfill etc... those I would like to be members of because they are important to me which they remind me of important things. So the groups that request my joining their membership, I'd kinda would like to know 'why'.... so I suggest this idea, which you may feel free to disagree, agree, state your own opinion... whatever.

I would think that it would be a good idea to have a feature with your "requesting your membership" to give a very brief explanation why the admin is seeking your membership. NOT joining if it is an open join thing. I think there's one for a admin accept/deny membership request, but it would be nice to have one when you are requesting someone to join your group. I'd like to know why you want my membership.... briefly explain why...

it is important to me that you should join my group for such and such reasons. That is it.

Couldn't you just comment the group owner and ask?

sure, but that means you have to go type in the username in the search subeta and click on it and find the comment box if they have an awesome profile.... just seems like offering a brief reason would be more efficient imo. But then again, this is an idea and open to other's opinions and suggestions. So thank you for your suggestion.