This. There's a reason why they almost always put the triple-car garage out in front as the most prominent architectural aspect: "Hey, look how many cars I can have."
Better than "McMansion" even is "Faux Chateaux"
(Having a big spacious home is not something I'd safely criticize as I have 6 acres and a house a bit too big for the family. The simultaneously ostentatious and ... ugly... yeah)
It's often other reasons, usually because the house is designed with a single garage and there's an "upgrade" button available.
It also makes the house fit on a smaller lot if the driveway is straight to the road.
Most if not all McMansions are builder's specials designed to be sold and upsold; often if you go to the builder's site you discover that the lowest end version of it actually looks pretty sane, all things considered.
Better than "McMansion" even is "Faux Chateaux"
(Having a big spacious home is not something I'd safely criticize as I have 6 acres and a house a bit too big for the family. The simultaneously ostentatious and ... ugly... yeah)