taking a guess here it may be because some mental disorders come with a situation where in the heat of the moment someone wants their account deleted and then when they calm down they do not.

another guess is some people have mental disorders where their alters may request the deletion and the others host and other alters do not want the account deleted

another guess may be because some people in the past have posted they wanted their accounts deleted just to see who is going to beg them to stay in other words for the attention factor.

taking time between the request for deletion and the actual deleting Im guessing may be a way to weed out these problems by...

giving those requesting their accounts to be deleted time to calm down work out their problems that may be causing them to want to delete and weed out the ones that are not serious but rather for attention threads. to give those with DID and other disorders that may interfere with having accounts time to make the decision...

so that in the end the ones that really want to get deleted do.

these are just guesses mind you. to find out why its taking so long to get your account deleted you will need to contact the moderators or administrators or owner of the site.