It's not that they are generous but they are doing this intentionally to lure the people to visit them and play on their casino. Eventually, people will get hook and use their own money especially if they are winning on their early tries. Casinos can always recover what they have spent on their promotion because most of the players are going to lose.
It's obviously luring new users and that was usual. The important thing here is, they are offering bonuses when you registered.
Seems not good to try a gambling site for the first time where there are no even benefits or advantages we can get.
If new sites won't offer such promotions and bonuses, expect they can't attract new users to their site. That was a necessary thing to do in the marketing field.
Business is business they always do this to earn more profit and invite others to join their platform. It is only you if you want to get persuade by them but still it is a bonus which is free money (but still you can lose it) and it will trigger you to deposit money to play more. I remember those crash games that I've played and its my first-time , they have daily faucets which I thought i wont be get persuaded by those promotion and wont deposit money but after a day I'd deposited my money and lose it all.