Well, several of us do - I'm not exactly sure how many because I don't know who all the smaller pots belong to, like, are those people who also have a box, or additional people who are just using pots but in the same garden area? There are also some folks who have planters up on the railings higher up in the courtyard (I'd like to do that too but haven't had the money to go buy railing pots). Many more of us also have plants on our balconies, but I genuinely don't know how many of us are gardening in the courtyard. :)
A couple downstairs used to garden two whole plots (the bigger areas that our garden boxes and pots are in) that beautified a whole section of the courtyard, and there are of course plants still there now that are perennials, but they haven't done their usual big planting of additional annuals this year; however, I know that they have been living through the remodel of their apartment rather than switching apartments like I did, so I think that's why, it must be exhausting for them!
So several neighbors do contribute. I think it's more likely those of us who have lived here a while, whereas some tenants are just in and out for one year or something.