Where has "Unlimited" come from? Nothing here is unlimited, nor is anyone suggesting it should be. Can you explain?
Unlimited vs. Limited-Use. Meaning, mechanically, at-will/automatic vs. short or long rest recharge. If an ability is limited-use-before-a-recharge, that adds a tactical dimension to it (do I use it now, or later), so if tactics is what you're angling for, something that is short or long rest recharged would be more appealing than something that is used whenever you want or is used based on a random die roll. Meaning that a tactical player opts into short-rest-recharge abilities because these are more tactical and thus ENJOYS the psychological play of "Do I use it now and not have it later or do I save it for later and muddle through right now?" Someone who doesn't like that question isn't as interested in tactical considerations, and so goes for ol' reliable Critspam McGee.
The DM designs the adventure and circumstances, and is the main person responsible for whether Short Rest occur.
My position is that the DM doesn't dictate when rests happen (ie, it is the players that declare the action), she merely gets to veto it (ie, she can say "the smell of your cookfire attracts goblins"). Which means that the main people responsible are the party members, who decide for themselves when they want to try and take a rest. The DM merely sets the context in which that can occur (and she may set it so that short rests cannot occur). In the same way that the DM sets the context in which attack rolls or climb checks can occur.
Party members should generally have an indication of what circumstances will allow them to take an hour rest (DMs who constantly spring ambushes are jerks just like DMs who constantly take you captive or have the villain escape or have the NPC's death be inevitable are jerks), and they'll be able to plan their approach to the adventure's goal around that indication. If you can't take an hour break in the middle of a goblin warren, then you're going to approach that warren with the idea of "lets not fight ALL of them before lunch, okay?"
Your "Long Rests must be truly a hassle" doesn't make sense. They're an "end of day" thing and can be achieved by leaving the area of danger, which is unlikely to be practical in the same way for Short Rests.
The context for the long rests being a hassle is that if you can't take an hour rest, you REALLY can't take an 8-hour rest. So if you can take one, what might prevent you from taking the other?
You say that it's impractical to leave the area of danger for a short rest, but why?
Why can't you leave the goblin warren for an hour, or hole up in the goblin store room for an hour, or break for lunch on the road for an hour?
I mean, even armies on the front lines in World Wars could find some time to eat or sleep or write a letter home. And they didn't have
Leomund's Tiny Hut. If the fighter needs a breather, lets stick the elf as lookout in this quiet corner of the dungeon where the goblins don't go because there was an ogre here (until our swords had something to say about that) and take a breather.
In fact, that's part of what I *like* about the longer short rests. It is something you have to actively go DO, it is an action the party takes, and it has to be considered in the context of achieving the party goal. If your desire is a smash-and-grab geurilla strike to grab the MacGuffin and go, you need to maybe sneak past some encounters you'd otherwise tackle head on because you can't tackle them all before you need to rest (thus allowing them to escape). If your desire is to exterminate all of them like it's some sort of goblin progrom, you maybe make quick forays into the warrens and post lookouts who can let you know if they're trying to flee (thus wearing them away over time, like a siege). It's adventure-based design at work, where the goal isn't to Have Encounters, but rather to Do A Thing, and the encounters are just some steps on the road to that, sometimes steps you want to (or have to!) skip.
It's also likely worth mentioning that 5e is generally much more comfortable with characters not being able to use their special shiny things than 3e or 4e was (while not being quite as negative as 2e could be). Even if no one could ever take a short rest, and no one ever used a limited-use ability, the party would still probably be able to muddle through most of their adventuring day and still even retain a flavor distinction between high-damage/high-accuracy weapon users and low-damage + special effects spell users.
Ultimately, I don't expect every character with short-rest-recharge powers to hoard them for fear of not being able to have their character take a lunch break. Rather, I expect that this real "down time" cost will make them think beyond the individual encounter into the adventure context in general, and that's something I
want in my games. And for those that don't, I'm sure "a short rest is 5 minutes" is part of what WotC expects to happen, even if they made a different default choice.
