Do bingo halls cheat? Can you give an example how they cheat?

If you are a bingo player, I am sure you are familiar with TEDS or computerized bingo. You pay $15 dollars for each computer monitor, which supposedly has 72 cards in each. I find it extremely amazing that each person normally has one TED he/she is playing. If you play two machines, that’s 154 cards. If you play 10 TEDS, that’s 720 installed, computerized cards for just one person. Question: with all TEDS being played with 72 cards in each, then how come each bingo game just has one or two winners? Shouldn’t there be muliple winners with all those computerized cards being played? The computer, which operates the TEDS, is normally hidden somewhere in a back room or in a corner, out of sight of the players. Should’nt this arouse someone’s suspicion of cheating? Why does each TED have a house-written number on each monitor sold? And, how does one know that maybe only five cards( for example) are being utilized, for play in each TED, instead of the installed 72 cards? Did you know that bingo halls normally only hire family members as workers? Why is this?