texas doesn't require a specific r-value for walls in the southern third of the state. (the rest it's r-5). They do require some insulation in an attic.

Most (cheap) homes don't slap up insulation if they don't have to. and r-5 is an extremely low value.

and further, that's only on new houses. There's plenty of old houses still in circulation and the vast majority of the old houses are entirely uninsulated. a properly insulated house, you can keep rooms warm just by being in them. we saw that's not true of homes in texas during the big freeze a while back.

Its not just about keeping heat in in the winter, its needed to keep the heat out in the summer.

that's this sarcastic comment was about:

(Why would you want to insulate against heat, right? global warming is a woke-ist hoax! /s)