That number is the total who have joined since the start of the site. The biggest majority are no longer here for various reasons. Most have gone on to other sites, been suspended, are puppets.....etc.....
I believe a competitive new start up site started sometime back, swung many members that way. There may still be members here, but spend more of their time there. As every site has it's own identity and characteristics, some like other sites better.
I think you are absolutely correct, few really active members. I find this site to be a bit cliquish and not really apt to go anywhere in the short term. JA, the owner has worked very hard and deserves all the praise and credit in developing this site. Although this site is presented as a member involved site and more of a family type community, it's limited to her final thoughts, as it should be. In other words, you will either like it here or not. You will be part of the family oriented community if you follow ToS closely and don't rock the boat. This boat floats, just as the tides rise and fall.
I think that's pretty much the same on other social sites. I belong to another smilar site and the same thing has happened. Between the witch hunt for socks and trolls and a group of members considering every new member an enemy, I would be surprised if they have 50 active members there any longer. The same members post questions and the same members respond. If enough other members block you, your exposure is even more limited.
Benedict Arnold 