1) They are NOT paid for by the spectators; it hasn't been that way in years. They are paid for by the promoters, who bankrupt themselves in doing so. If they truly were paid for by the spectators, they'd be riding for 7 quid a night...
2) They USED to go out to entertain. Unfortunately, speedway has gone the way of many other sports, and the only thing that's important to most riders is making money. Oh, and pretending they are some international sporting superstar.
3) Readjusting chains is NOT boring. In fact, it can compare quite favourably to some of the racing I see...