Going to comment my experience on this one since so many others have too. Same experience as everyone else commenting on it and will give an example of doing it along with the scenario where it happened most recently..
I'd love to run a bunch of 5e-only gamers through 2e style encounters, such as warbands of 6d10 goblins. (From memory. I vaguely remember some goblin encounters were in lots of d100s)
*Five players with level 5-6ish PCs were three encounters (maybe 2) and an equal number of short tests into a lowish level adventure involving a possible necromancer kidnapper with zombies and refluffed undead hounds of some form. Nobody had been particularly injured and they literally were given a full 3.5 style 50 charge CLW wand during session 1 at 1st level which they refused to use on account of "we might need it more later and the merchant who [literally] gave it to us might expect us to do the job he said would come next time if we want another" but they refused to use it anyways. The rest loop was to endlessly recover fighter action surge warlock pact slots and monk ki spent at nova rates every turn so far.
* Players decided that they were going to hole up in a storage shed/barn of some sort for a long rest after barricading the door. The structure in question was A:behind the gates B:inside the walls and C:surrounded by the necromancer's forces... Some of those forces were already seen by players)/PCs across the compound but the undead (zombies and such) had not reacted to them.
* I pointed out all of the many reasons why this was a colossally bad idea ranging from possible survivors to the necromancer and variety of (un)seen undead likely to react to the recently slain undead the players had already killed and left behind.
* Players decided that pulling up the ladder and sleeping on the second floor of the barricaded barn or whatever while knowing A B &C would be more than enough to get back to full.
Not only did the players choose to do nothing and finish their rest when they heard noises at the door then heard more noises outside.... They were angry that finishing a long rest on the second floor of an eventually∆ burning barn that had been barricaded from the outside was bad for their health and demanded me to produce a rule for that (debuffs? Exhaustion? Been a while). They totally lost their minds when they got outside and found levelup5e squads of zombies presenting an actual threat.
∆ wasn't a gotcha, "we finish the rest"> you still haven't finished but smell pitch and know it's sometimes used in arson>ok you ignore the smell and keep resting but you start smelling smoke and think you see/hear fire below>really? Okayyyy... Having been told the risks you continue on with the rest. Lucky dice roll you finish but picked y[debuff or whatever].