.. it is obviously for newcomers who will look into that but I don't think it was a good idea and I don't rely on such promotion but to consider most on their legitimacy even they can't offer those freebies, free spins.
Quiet disagree that it's only for attracting new players.
Didn't you know that free spins are very important and a big deal to those who always play slot? Not for casual players but to those die hard slots gamblers. That 5 or 10 free spins when got hit is almost a bet-saver especially when the funds are now in critical status. And sometimes, free bets can result in good winnings. With the continuous free spin, it might give reasons to a gambler to stay with the site for a long period.
But yes that in terms of promotions, shouldn't rely on it for checking the legitimacy of the said site.