That's normal game behaviour. There is a hack here: http://www.moreawesomethanyou.com/smf/index.php/topic,7.0.html to enable community lot skilling. If you want it, click on the link for the most recently released expansion you have, then hacks, then scroll to comm-skilling.zip. This is what it does:
"Controlled sims, NPCs, and townies may gain skills while visiting community lots, including non-college community lots. Notifications of skill-point gain will only be displayed for controllable sims. Enthusiasm may now be gained on community lots and while visiting."