Maybe (especially in Sweden where they like to see less people gambling and reduce harms by these regulations like ban bonuses etc..) one reason to take tax from GGR is make gambling less tempting by stopping players to make any "extra" deposit what wasn't planned but just because casino sent out nice promotion.
Also in UK promotions need to follow quite strict guidelines by ASA (?) or who ever, offers shouldn't create any urgency to make you deposit now or it's too late.. For some players these kind of promotions what players like as getting something extra, are one way to spend over their means when surprise email in your inbox trigger you to make "just one deposit" more even you didn't plan for it before next week.
Yeah, thats absolutely the reason for the bonus-ban.
I have not seen any numbers, but im guessing its probably a pretty effective move to stop those spur of the moment deposits that can happen when you get an email or text with a decent offer.
Still prefer it how it was before the regulation.
Sure, i may cashout more often now that all my deposits are raw money, but my playtime has been reduced since i cant take any bonuses. And if you have a shitty month, the gambling-budget goes flying out the window waaay faster.
Overall i spend the same amount of money, but get less playtime.