And the usual incentive is writing the adventure so that resting every encounter is either tactically unsound or leads to undesireable outcomes other than their personal deaths (aside from the primary pressure of the presumption that the players would find this boring and show up to play in some manner conductive to the DM's game, because tabletop is not a videogame). And as you have already acknowledged, it's likely that your players do not consider optional objectives optional, which means that adventures with otherwise "soft" limits are actually hard limits, and if you wrote them, that's your adventure pushing harder than the players want. Not the DMG.Which is of course, nonsense. In D&D the tactical choice, from the parties perspective, is to always go nova and then rest after every encounter.
I have always seen it as the DM's responsibility to give the players incentive to follow them, but I suppose that is a bit of reading between the lines.
Looks to me like they were saying that it was your idea to go 80% per day every day, which is not in the DMG. Their specific line is "you make it a struggle to get anything." The second part of their post, which you acknowledged, clarifies this.That was specifically in response to someone saying that it is I, not the DMG, that came up with the idea that players should need to expend resources, and I was pointing out that not only does the DMG say that, it actually takes a step further than I ever would by saying that something MUST require resource expenditure to provide XP.
And my further response is that your insistence on rewarding xp for any sort of combat incentivizes the same nova tactics you say you want to discourage. If the PCs have a one-sided fight because they burned an entire day's worth of spells on a chump and then went back to sleep, and the DMG explicitly says that favorable/unfavorable circumstances modify xp awards, why wouldn't they get less xp for that? If you give them full xp for going nova, of course it would seem unfair if they got no xp for "flawless," (which is actually "lucksack" or "were never actually at any risk." If you don't want people to play like it's a videogame, then don't give out guaranteed minimum rewards like one. Getting no xp for a "fight" where you were never at risk isn't harsh, it's the only sensible result.
The same solution applies to the "hunting for xp" problem where people will go searching for a random encounter to push them over the level like its a videogame: so don't give them xp for it. Xp comes from practical experience and accomplishment of goals, randomly walking off into the woods to lob a Fireball at a bear furthers no goals and actively reduces your ability to continue with what you're supposed to be doing. So it gives no xp. Because the DM decides what encounters are worth xp- the justification is just gravy.