Part of the promotions like this is to not let people know that there are terms thats how gambling site mostly attract people with their so called generous bonus. Of course the term is visible but for some people , they will never check it and then when they deposited they just realized that they cant withdraw unless they wager specific amount

In that case those people are pretty stupid. You should always check any terms that may be applicable, especially when it comes to money and bonuses.

No need to act like casinos are evil for offering these bonuses either, as that's not really the case. Believe it or not some people gamble for the enjoyment and to relax for a bit and in those cases any and all bonuses help out more often than not.