Yeah, the casinos know this, and they of course try to make the gamblers stay as long as possible.
At the end of the day making money is simply convincing someone else that they should spend the money.
It's all about how they feel really. And casinos have perfected this feeling of having the chance of getting rich by paying some money.
Unfortunately for the gambler though, the more vastly common scenario is that the only people getting rich are the casino operators.
Perfect ways to do this in online casinos are daily / weekly and monthly bonuses that you need to login in order to cash out. And some of them distribute dividends (betfury) or airdrops (shfl) slowly, so you can click often if you want it and get smaller amounts. Technically people could just wait until they are big enough and cash them out any time they choose, but some people are impatient and want to cash in as often as possible so they can gamble small amount as often as possible.
I am guessing that's the reason they don't just offer yearly or montly huge paybacks on those, because people would just rather cash them out.