I must admit I have never seen the evidence but have been led to believe that for some, VIP's/High rollers are their bread and butter.
Takes a few low rollers hours to spend what a high roller can do in minutes.
That's true and used to be much more like that some years ago, now as we all probably have seen from various threads here, quite big penalties given to casinos and probably many experienced as well, loads have changed in last years. We don't have to travel too many years back in time when things were really different because of less regulations and monitoring.
You can't really accept big deposits without any SOW verifications to know how these deposits are funded and sometimes (quite often actually) it comes up that your great VIP player is playing way more than sustainable amounts based on their income, then when you see bank statements where are loads of payday loans and other things which are not really pointing any healthy way to gamble, you as casino have to react these and limit or even exclude players.
Some casinos pre-set limits to player accounts (especially certain markets like UK) just to make it easier to monitor player activities and make sure somebody can't blow their whole year income in few hours etc... I think it's a "healthier" way to enforce some limits which are maybe based on countries average disposable income or what so ever and if you wanna play £30k in month, you need to show that you can afford it.
It's after all quite small amount of people who can afford to lose lot every month, that's why also some countries (i think UK included but too lazy to check) have made rules that before you can make player VIP, you need to complete SOW, which kind of makes sense. Being VIP is just so important for some people that they really might end up to spend more than they can afford, just to keep their status (which is again not really healthy gambling).
I personally would prefer to have huge amount of low rollers instead of few VIP:s, risk is just so much smaller and you hardly can get trouble if some grown up person spend few hundreds on some month vs somebody spending £30k/month and now as we have seen, casinos do actually get penalized from accepting crazy deposit amounts without verifying where these are coming from (and unfortunately in some cases problem gamblers been stealing big amounts from work etc...).