If you have an interest - say Short Sales - it helps to go to GROUPS at the bottom, right of the links on each page and do a search for 'short sales.'

When you find that short sale group, the most recent posts pertaining to the subject are there. You can read all posts pertaining to that subject. 

I feel like a lot of folks do that with Bananatude posts as well as Speechless Sundays posts. 

I continue to use them, feeling like some of them are a good point of reference if I'm ever on a hunt for a specific topic.

All I know is I joined them because of like-minded themes and subject matter. They are (or were) fast lists of topics you enjoy reading about.
I belonged to several that never interacted and I dropped most.
I think many of the group founders have dropped off ActiveRain.
That said, Anna Banana Kruchten Phoenix Broker and Myrl Jeffcoat both have groups I get interaction from and group featured in regularly, they make theirs fun to belong to and I like the bloggers that post in them.

Debe Maxwell, CRS explained. 

Most groups are no longer moderated. 

While I do not moderate the market report groups I created over the years. I do moderate Craptaclar!  Mr. Crappy would not have it any other way. 💩

I belong to a limited number of groups. Can't say that the interaction I have on my posts comes from the groups more than from the blog roll. Too many groups on AR and need to be culled as many are very inactive the last time I looked.

Just another way to group posts and possibly gain more viewers.

I kind of wonder the same thing.  I think they used to be good for SEO, but SEO through the Rain went by the wayside a long time ago, haha.

from a SEO standpoint, no, from a group where posts are about a certain topic if you are looking for something, yes.

I echo the previous comments posted Peter Mohylsky 850-517-7098 I still post to All Things Florida Bannatude Olds Farts Club When you tag the group you may connect with folks you never knew existed.  Yes, many groups need to go but the ARMS is working on more important things like restoring the evergreen links😎

In addition to ones mentioned by Thomas J. Nelson, REALTOR ® e-Pro CRS RCS-D Vets 

there other active groups like:

Old Farts Group, Crap-tacular, and Bar Tender Make Mine A Double. 

I enjoy posting to groups because I usually get a boost on my posts when they are featured Peter Mohylsky 850-517-7098 

Hello Peter, I know I am in the same groups and should look if there are new ones I should join.  Good question

Originally, I thought it helped with SEO and recently have wondered what the benefit is.

I am down to one group.

Time may be better spent by focusing on Facebook groups if you wish to participate in groups that share your interests.

I am only active in one group at this time but there are a few others I should consider and I have no interest in SEO at this time.

You are enthused in a certain area of real estate, marketing, whatever. It helps to have a group that has the same zest and fire in their belly to grow and learn together. Often, when you ask a question now looking for input in Q&A, you don't get the helping hand input that groups can provide. 

I haven't really attached a group on any of my posts for a very long time.   

I no longer believe so. Most groups no longer have a moderator to point out the newer posts that come up in the group. Some highlighted ones are eons old.

Only one I used was Market Reports so I can see what others are doing (style wise) & how they present their info.

I use tags to find older posts.