Ideas
I have the same problem, except that NOONE comes to the lots when my Sims visit. I do have mods but I did the 50/50 and it's not my mods. I did a repair on the game and even deleted the sims folder and had the game recreate it but I still have this problem. Even in a new save with no mods at all.
But I have to mention that I have all of my community spaces as the default community space (i just have all the items for all spaces in place) because I don't really want the spaces to be specialized.
Now, what would normally happen is that vendors would show up to sell their stuff on the selling tables, and lots of Sims would come to do their thing, garden, chat and use other activity objects available. If I have a food vendor stall, an NPC would show up and start selling.
But now when my Sims visit the lots they are completely alone and NO other Sims enter the lot. It's like the community lots have all become generic lots.