One of the key reasons why so many online casinos offer players no deposit bonuses is that they benefit both the player and the operator. If the offer is deemed to be good value-for-money, the casino gets good advertising and is likely to attract more new players than brands that don’t offer any new player incentives.
In return, players get more funds to play (and hopefully win) with. Another benefit for both sides is that no deposit casino bonuses give you the opportunity to see whether the site meets your needs before spending your own cash. You could liken it to test-driving a car! If you accept the offer and like what you find, the casino is likely to benefit from your custom in the long-term.