Yeah, you pretty much nailed it on the head. What they are doing is "cherry picking". They are picking the EASY fights, that even Ray Charles could pick right. Anyways, all they are doing is lessening their chances of being top point leader and top point event winner. Therefore, they can keep on trying to perfect their record, because it gives you and I a better chance of winning REAL money! $100 for each event you are the top point man/earner, and doubled if you are a premium member. The funny thing is, when I started out on this site for some reason I thought it was required that you made a bet on every fight. I don't know why I thought that.
Anyways, to answer all of your question, no you do not lose points for not picking and you could still be top earner without making a bet on some events/fights. You could bank off of one fighter and not need any other bets. It really depends on your situation. Hope this helps and good luck with the rest of the season!