Claiming free bonuses with high wagering requirement from casino to other casinos will be wasting your time and energy only imho. The probability to complete the wagering requirement is so low, so taking it for fun only on your spare time is better instead of forcing yourself to claim it everywhere.
What you are telling is the true fact of bonus given by the casino or gambling sites, as they know that it is very hard to achieve that wagering reqirement and out of 10 person 1 person claiming the bonus with required wagering itself is very hard. That is why all gambling sites and casino sites are giving high bonus for all new and old customers as they know in the process of wagering bonus the gambler will also lose the deposited fund in the end.