I grew up living out in the sticks and in a household with no spare cash, and a SAHM. So takeaways were almost non-existent.
In my case, I live in the city but still have a 45-60 minute commute each way. DH and I both work FT in stressful jobs. We have more disposable income than our DPs would be used to. We can both cook, pretty well. But there are nights we do resort to the takeaway for reasons mentioned above (cold, tired, wet, fucking exhausted, DD being a pain in the ass and not eating what's in the fridge, don't fancy whats in the fridge ourselves, very short time between commitments etc).
Leftover food gets used up mostly - we freeze a lot, get creative on other nights, eat tonight's planned dinner tomorrow, etc. And we often freeze the 1/3 of a portion of curry that might be left, which DD will have for dinner another night that she doesn't want what we're having. We actually throw out a LOT less than DMIL does, and always have done.
DM gave me a lecture the other night about "staying safe" getting the train home from a Christmas do. I was getting my usual train just later, from my usual station, late evening (8/9pm) rather than late night, and I am always ready to get a taxi if I've had too much to drink or feel in any way unsafe. But I have been looking after myself, and using a lot of public transport, since I left home in my early 20s (so more than 20 years) and DM just cannot get her head around either not always getting a taxi OR (preferably) DH coming to collect me (when DD is at home asleep in bed). She also got a shock when she realized we don't drop or collect each other from the airport - DH travels almost every week, and I have a reasonable amount just now again, both at unsocial hours, and we are perfectly happy to either drive ourselves, get a taxi or use public transport if timings suit - rather than get DD out of bed at 4am! But they are used to driving everywhere, whereas we are used to a balanced mix of transport as cars are really not great into the city!