I'm in the US.

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.

Yeah, I'm not opposed to taking leftovers home if it's something I would eat the next day (like Chinese a lot of the time). But most of my leftovers are usually piles of carbs that I'm unlikely to bother with.

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.

seriously? like, even if i'm heading out after dinner, i just leave the leftover box in the car. if it goes bad, then it goes bad, if it doesn't, great! lunch for next day.

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.

Take "fully loaded nachos" as an example. After a few hours, the chips are really soggy and gross. And a good steak, rare to rare++ (or even medium rare) is delicious when it first hits your plate. But once it cools down, and you reheat it at home it is completely different (you end up not getting it warm enough, or it gets overcooked).

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 just leave the leftover box in the car.

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.

Food shouldn't be left out unrefrigerated for more than 2 hours, is the USDA's recommendation, otherwise the bacteria can multiply to dangerous levels. Even if you eat it later and don't get sick, it doesn't mean it wasn't a risky thing you did.

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...

Food safety is a lot more complicated than time and temperature. Guidelines like the USDA's are simplified and overzealous to the point of harm IMO. Leftover pasta in tomato sauce in a takeout container in a car overnight has probably never made anyone sick. Pasta in cream sauce might spoil, but again probably perfectly safe from the standpoint of pathogens. Meanwhile, a raw lettuce salad stands a reasonable chance of making you sick even if always stored according to the guidelines.

If you're going to eat it, you've got up to 4 hours. Two hours is the time to get it out of the danger zone if you're going to leave it in the fridge. But if you're going to eat it rather than store it, the guidelines are more lenient.

Have a source for that? I can't find a mention of that anywhere.

I apologize: the USDA uses only the 2 hour rule. The 2/4 hour rule is common in most of the rest of the world, most prominently in Australia, e.g.: https://timestrip.com/2-hour-4-hour-rule-haccp-plans/