The problem with tipping in cash is those tips dont get shared evenly, just the person who interacts with you directly.
It takes a lot of people for that one waiter to bring you a drink, he/she doesnt go make the drink, clean the glasses, buss the tables (sometimes) etc.
Apply this to your rooms and other tips, unless you go around asking who all helped make this drink and tip each one, if you remove prepaids you are shortchanging people.
(Yes i know, bars add a prepaid per drink, just an example, choose MDR or WJ as other examples)