A short while ago (by historic standards anyway) You couldn't keep your lunch hot or cold for hours on end. Sure you could pack up a lunch in a pail, but who knows what temperature it was when you ate it. Ona hot day, prolly super hot, tin pail, lots of sun...In the winter prolly frozen, tin pail, ice and snow around...

So either you ate it the way it was, or you devised some odd way to keep it cooler/hotter. Like burying it with a hot stone, or by the fire, (good way to lose it/get it burned up) or you let it drag in a cool stream (real good way to get it eaten by an animal of sorts.) In general you had a bit of a problem. but if you needed to be working all day and didn't want to walkk hom, you suffered.

Nowadays we have coolers that will keep ice frozen for 24 hours, and insulated thermous' that will keep hot foods hot for 12, so why do we hardly ever pack real food? Oh sure you see lots of people packing pop and potato chips, but how often do you see someone packing dinner? or lunch. One that doesn't come out of a vaccum sealed bag? What is the point of all that tech, if it is just used to keep ice umm ice?