I feel like your examples here were so incredibly simplistic that it's not worth arguing with. I dunno what you're playing, but in my experience most adventures don't last exactly one adventuring day and have a clear last fight in the way you're describing, so being really sneer-y about this and calling people "braindead" just seems out-of-touch.
Y'know what? I'm going to call it out. Not only are my games that I play friendly to the Barbarian's Frenzy mechanic, I bet your games are also friendly to the barbarian encounter. Um, general "you" that applies to the majority of people on this thread but possible including Ruin Explorer
Well, a typical adventuring day is 6-8 encounters. If you're like me that attempts to run this, your encounters will run up to around medium or hard. It's obvious that the party will probably blow past the first and second encounter, after the third, players will start attempting short rests. At the fourth and fifth encounter, your party is struggling and they're running out of resources, so you rage on one of those encounters. On the sixth, seventh, and eighth encounters, your party is significantly spent from attrition, medium encounters suddenly feel threatening and hard encounters might knock a few PC's out. You'd have probably raged once more before and when your team desperately needs the damage, you can frenzy. If another unexpected encounter happens, use your best judgement but you have another frenzy opportunity.
But I doubt most games here are like that. There's probably 2 hard and 2 deadly encounters in an adventuring day at the most. Of course, it kinda wonks with the balance of spellcasters and martials but with less encounters and they're more swingy, Frenzying once becomes even better in this style. You get to be frenzied without much concern 1/4 of the combat encounters rather than 1/8. Plus, players will quickly try to long rest before the third or fourth fight anyways because it was an incredible and quick tax on their resources and they're fearful of an even stronger encounter.
But let's talk about afterwards: most games have moved from exp to milestone for some reason or other. This means that combats aren't worth much but an HP drain in the player's minds. This also means they're going to want to finish the quest as quickly as possible since there's no incentive to stay longer than they have to. Most adventures in homebrew games are probably 2 or 3 days consecutively.
Probably less, since there's usually the walking montage in-between so that the actual adventure takes place in a dungeon, which is usually cleared in a couple in-game hours. This means that most campaigns are structured: hook, travel (1-6 days), dungeon, travel back, completion. You get plenty of resting opportunities in the games.
In modules, it's even better since random encounters are usually just once a long rest anyways.
