You couldn't get free bets easily some of them were given to existing players and others were literally a free bet that has no value and was used to test out the website but there are some that has a free bets but there is a wagering requirement needed before you can withdraw it or convert it to a real balance. I'm not sure which bookies have free bets right now but you can check them one by one and check their promotions page.
Well that is why they created their own token, just like a FUN token.
It is rare in most casinos that offer that kind of promotion because that is equivalent to the money that has value. But I saw also a casino that has free bet after you will desire the desired minimum amount and I think that was very common these days since gambling online is very in demand and popular wherever you go. To avoid a possible problems, you perhaps read the TOS.