That's not the problem. The problem is actually pretty deep. Short rests were supposed to fix the five minute adventuring day, but they haven't done that at all, and the 6-8 encounter recommendation carries it's own problems.
1. Encounter require time to play, especially if you use a battle grid. 6-8 encounters means setting up 6-8 encounters. If you're only able to play 3-5 hours a week, it's actually somewhat reasonable that you don't have time to fit in 6-8 encounters unless you're literally running 6-8 connected rooms. Yes, even if they're at half difficulty like 5e encounters are. Sure, you could use two game sessions to split one adventuring day, but my experience is that few game groups do that. Most game groups want to start a session at the end of a long rest so that they don't have to remember their character state from a week or two ago at the start of the next session.
2. Because 5e encounter difficulty is heavily lowballed, 6-8 encounters can be extremely easy, not challenging, or not interesting. In some groups, the players can feel like combat is a waste of time in a game primarily about running encounters. This means the group will just run fewer, more challenging encounters, but this has it's own problems because it eliminates one of the ways 5e tries to encourage you to short rest.
3. There is no reason to short rest. Or, rather, there is no reward for not long resting and playing through more encounters in a day. Since the game still has attrition elements like long rests not recovering all hit dice, the cost of a short rest is often not a lot lower than the cost of a long rest. Since a long rest does everything a short rest does and more, the only reason you ever really need to short rest is when you're under time pressure, which simply isn't appropriate for every adventuring day in every campaign. Worse, if your campaign has real time pressure, then you often run into situations where the players can't short rest, either!
Yeah, all of this!
1. Is particularly important, because 6-8 encounters really is a hell of a lot of time, and it feels like 1 day = 1 session is kind of how D&D should work, at a minimum, if not more than one day per session.
It kind of just moves the old 4E problem around. 4E had the problem that, especially as you leveled up, combat took a really long time (3E had it too, arguably worse, but that's a more complex discussion so let's stick to 4E), and so a session could easily be dominated by, say, two combats. Usually they'd be pretty engaging and everyone would have a good time, but it still felt a bit messed-up when a 3-hour session was basically two 1hr+ combats.
5E shortened combat massively. In theory, you're down to like, 15 to 30 minute combats. Except, if you're supposed to do 4+ of them per character-day (assuming maybe another 2-4 non-combat resource-using encounters), you may well end up in a really similar place, just instead of two combats dominating the session, four do. The same issue is prevalent, just slightly more broken up. It feels a bit better, but not a whole lot better.
And yeah re: 3. I've noticed that whoever is DMing, whatever the adventure is, whether it's homebrew or pre-written or whatever, the number of situations where you can safely do a 1-hour short rest, but not safely do an 8-hour long rest is pretty small. It's not non-existent, but it's small.
EDIT - One of the DMs I play with is remarkably good at getting 6-8 encounters/day and making it feel legit, and not run on too long (he's not even the most experienced one), but even he cannot reliably create situations where short rests are viable and long rests are not. Instead it usually ends up that neither is, because an hour is a bloody long time to take a breather.