Around here a lot of people have 2 doors on a 2-door garage which means you can't park say just one car in the middle, and you have to be very careful or you hit the post between the garage doors. I think builders build them that way to save, .... How many dollars would they save? ... so they can sell them cheaper, and people buy them because that's what's available.
The suburb where I lived in JHS and HS everyone had 2-car garages with one door**, so you could if you wish park in the middle and store junk on the sides, and never worry about hitting a non-existent post.
If you ever buy or build, it seems like the wrong place to save money.
Seems to me, two single doors cost more than one double door, 2 garage door openers definitely cost more than one (Even a bigger one. Do you need a bigger one for a double door? I thought if the springs are set right** it's not hard to lift even a double door.) but you save money on the lintel.
How much does it save to have two doors? It does save money, doesn't it?
** Our door was hard to lift, but I was too young and stupid to realize it could be adjusted, and my mother probably didn't know either, and she was too thrifty (and living on the money my father left behind) to pay someone to adjust it. We also thought all garbage disposals made a lotttttt of noise so she never used it. Decades later I realized the one we had was worn out. I don't know if it actually worked if you put up with the noise. The house did have a gas incinerator, but to save gas I think she left the pilot off and she just put in newspapers and lit the fire. But we lived a middle-class life and she sent both of to college (without our having to work during school) and lived 39 years on the money my father left. I'm not complaining. We had a good middle-class life.