They actually are obligated to do these checks for other reasons as well, not only to postpone your withdrawal request to be completed. You probably are not interested to go through all their commitments so here is one very short version from MGA (which applies you if you are from Canada like can be assumed from your profile).
Very short and simple guideline for ongoing monitoring of players and what you are obligated to do as casino operator. If casinos could choose, they wouldn't give fuck of your SOW as it's hell a lot of work but unfortunately they have to follow many rules. This was most simple and very short content about ongoing monitoring by MGA with some pictures as well so not much to read even, made very simple and basic what you have to know and what steps to follow with all your players. Casinos would be really happy not to have these at all, do you honestly think that they make more money than they lose in salaries of compliance departments and also lost customers who are not willing to provide requested documentation? Few inpatient players might reverse their withdrawals but that don't really generate such an income which would cover you all work and money attached to these monitoring and due diligence processes.