I'm going to play devil's advocate here and say you actually drink less if you have a kegerator. Here's the scene...You are hosting a barbecue. Kegerator is inside, the grill and party guests are outside. Beer in hand you go inside to get a (fill in the blank). While you're inside you A) gulp down the last 1/2 to 1/4 of the bottle in your hand because you'd have to come back in, in a few minutes to grab another one anyway. Or B) top off your half full glass from the tap because why waste a trip.
The same scenario can take place if you were watching TV, eating a meal, tinkering in the garage, etc. Fact is, within one trip, you just drank an extra half beer that you would not have if you owned a kegerator.
You can use this and to aid you argument if the wife is still nay saying...
"You see, hun. With a kegerator I would not drink as much alcohol and thus not drunkenly hit on your incredibly hot sister when she comes over"
"obviously, (wife's name). A kegerator produces far less waste than bottles. With less waste comes less times the trash needs to be taken out and thus less times you'll have to constantly remind me. I know how that upsets you....I don't want to see you upset"