It's probably isn't that important because there are more combat encounters than one per rest. 3 per turn means they would run out of slots 3x faster.
I mean, given how their system works, nothing is stopping you from having even MULTIPLE long rests after every single combat encounter, if you want to abuse the system, since there's literally no risk or drawbacks involved in spamming them.
So, yeah, it's actually pretty fucking important and fairly stupid in general.
But the stupidest thing is that they were recently on video jokingly complaining about how Metamagic "literally breaks the game's balance allowing multiple fireballs per round". Something that exists only because they did it wrong.
It's the waiter shitting on your plate and then telling you "Boy, this food we are serving surely stinks".