AKA's got it right,
The Casino is within its rights to impose any limits or restrictions upon their bonuses, it then falls onto you to either accept the terms that apply to the bonus or not take it up.
You will mostly find that certain casinos market to a particular region, players from that region are exposed to marketing and branding and thus tend to join the casino for the right reasons, while areas not targeted; may have increased wagering simply because a client from a non marketed region that happens to find the casino in question is much more likely to be bonus hunting.
These banned/increased wagering/restricted list grows and evolve based on recent and past activity both legit and illegitimate.
Anyway hope that helps at all, if you have any more questions feel free to PM me.
oooh btw not all Playtech casinos have such high wagering for the Netherlands *hint hint* *wink wink*
Cheers,
Dorian