A neighbor up my street has a bee hive but I think they no longer keep bees, I barely see a few bees but not in decent numbers I used to see. What a loss, I should drop in on them, if I see them, and ask about it. There's no activity around their hive box.
Sometimes, the bees will abandon the hive and follow the queen. Or, if the queen was killed, the swarm will also leave to find another colony to join. I know a lady here who is a beekeeper, and she has chased after her bees when she noticed them leaving. I'm not sure what the plan is when that happens; it's not like you can round them up and send them to their bee hive room, lol!
We've got 2 neighbors on our road that keep bees. One did lose his colony a couple of years ago and is trying again. The other has an active colony going on now. It is interesting!