3 cars garage is very useful if you have a family with kids in the driving age. Even if you have only 1 kid, you’re already talking about having 3 cars. If you have 2 kids, that would be 4 cars. That’s not considering if you starting having more cars per person, like a weekend car or a project car.
A lot of the space in a 3000 sq-ft house vs 2000 sq-ft house is just more of the same rooms. Bigger kitchen, dinning room, family room, bedrooms and that 1000 sq-ft fill up pretty quickly. If you love cooking, a bigger kitchen might appeal to you. I can understand people wanting 3000 sq-ft, but cramming 3000 sq-ft in a 5000 sq-ft lot is just ridiculous. A 1300 sq-ft house in Mira Mesa have a lot that size.