I don't know. I don't do that, though. Mostly because if I'm eating out, it's usually a prelude to night doing other things -- and the last thing I want to do is have to cart around a bag of food.
Also, I used to routinely take leftovers home. It was a habit my parents had, and I just did it unquestioningly. Then one day I noticed that I rarely actually ate the leftovers (they tend to not be terrific the next day) and would throw them away anyhow.
In any case, most of my restaurant eating is while I'm traveling so I'm mostly not able or not interested to do anything with leftovers.
and not sure how your food goes bad, if it's good in the restaurant... usually food doesn't go bad so quickly, but maybe you are one of those people who have some irrational aversion to leftovers (nothing wrong with that, my girlfriend is like that too) even though it's perfectly fine. right now i'm literally having reheated leftover pasta from a fine dining restaurant dinner last night, and i'm thoroughly enjoying it.
I have the same issue when using home-cooked food as leftovers for lunch the next day. Cube steaks are rarely good warmed over (they dry out), rice ends up losing its stickiness (so it is a wet mess, or dried out crumbs). About the only thing that I can use for lunch the next day is some pasta based dishes, pizza (depending -- again, deep dish goes gross after a few hours), and manwich or tacos is good the next day (gotta keep the meat separated from everything else so it is easier to warm up in the microwave).
I prefer not to have the food stink up my car.
> not sure how your food goes bad, if it's good in the restaurant... usually food doesn't go bad so quickly,
It's not that it goes bad, it's that it's not as good reheated the next day as something that I could just cook up myself, so I'll cook.
This depends a lot on what the dish is, though. Some dishes are OK the next day, but most aren't.
> but maybe you are one of those people who have some irrational aversion to leftovers
No, I have no aversion to leftovers in general, but again, it depends a lot on what the dish is. When I cook at home, I arrange my meal plan so that I can use any leftovers from one meal as an ingredient in the next day's meal.
So people that go out to eat then go out and do other things that night before going home, unless it's the middle of winter and the car is basically a refrigerator itself, probably shouldn't bother bringing leftovers home with them.
https://www.thekitchn.com/how-long-can-you-leave-cooked-food...