This may be jurisdiction dependant, but in the UK, the small prize fruit machine style games you find in pubs are required by law to payout a fixed percentage of their income over time. I believe it's 70%, but I think there are variations and exceptions to the rule.

So if £1000 is paid in during the day, the machine by law must pay out at least £700 in prizes. This is not allowed to be fully random, the odds of each game are not independent because they must by law ensure the minimum payout.

It's semi-common knowledge that the way to win at these machines is to watch them until you have seen someone else have a long losing streak, then take your turn when they leave as the machine is now 'behind' and overdue a payout.