They (majority of casinos in Vegas) already pool tips. It is a bad idea to pool tips with the people who are supposed to be in charge. Hence the oversight comment.
The video poker is some of the highest profit stuff. Something like 80% payout overall with say $2 to $3 bet every few minutes at least. Generally speaking, you have to be actively gaming to get a drink. So you cannot just drop a quarter in to get a free drink. Also most places restrict the number of drinks you can get complimentary based on a time frame. Sometimes this is state law, sometimes the rules of the house. To just make them pay, drives them away.
I can only speak to the casinos here as I am still connected somewhat, but cutting off the free drinks has hurt revenue when tried. The whole frigging point is to get them drunk, distracted, and confused enough to lose more than they intended. Subtracting the alcohol hardly helps.