That's the main issue there imo that casinos don't use too much common sense when starting ask very sensitive information. Some big ones rely on lifetime threshold have reach some trigger, no matter have it happen in 6 years or 6 days, you get same threatening...
It's not really rocket science to make risk assessment to players, you can see deposit patterns, game patterns, deposit methods, country and area player (even quite exact address what can tell you something) is from. With these you should be able to make decision that how big risk there is for money laundering or somebody be problem gambler.
When there is loads of transaction in short period, you assign higher risk profile to player compare to some who have been playing £100 monthly with you many years and have no remarkable changes to patterns and game play. There is quite much information available what people in certain countries earn, have cost of living etc... if you just want to get it, then you can make your judgement if there is something which is alarming. Then can ask to fill your source of income with explanation and if needed, send some proof of that but these big fines which have been talked and posted here as well, are really extreme cases where most of us probably can agree that casino should have done something with such level of spending...
We want or not, these are here to stay, if your profile don't flag anything high risk but you play like average player in your country should be able (even if there are some exceptions there and there but not often) to afford, you shouldn't be teased like these lifetime thresholds and if you state that you are doctor and earn £XXXXXX annually, you can afford to loose bit more than average.
Changes to patterns, higher risk payment methods, higher risk countries (not mean to be racist but it's one factor as well) can flag your account and still imo it should be checked if there is need to ask your SOW, if you fill form on site in question where is asked your occupation and income, it should be enough if they are in line, without to ask your last two years payslips or something..... making bit research would make this process much nicer for players and would still be enough to bust ML or RG players.