I think the 6-8 encounters is "this is how many medium encounters will exhaust party resources", it doesn't seem to be a requirement.
While that's possible, I do think that the designers
did expect an encounter:rest ratio of 2:1 in order to make short-rest abilities valuable without being stellar. If it rises to 1:1 (or even 3:2), short-rest classes start to noticeably out-perform long-rest ones; Warlocks have more total spells (all at their highest spell level!) than Wizards, and Battlemasters have significantly more bonus dice added to their damage than Paladins. If it swings the other way, falling to 3:1 or even 4:1, the short-rest based classes become stretched excessively thin: a Warlock might only cast 4 spells all day (compared to a Wizard's 13 or more, three of them at max level!), a Moon Druid can only be in animal form for half their encounters, and a Fighter is (by the numbers) dramatically worse-off than a Paladin (getting half as much 'bonus damage'--if even that much.)
And the books certainly don't
talk about it like it's just a point of reference--it seems pretty clear that that's the "expected" situation. I mean, the devs
did specifically say that they wanted people to be levelling about every-other session from 3rd until the low teens, didn't they?
Perhaps, in light of the "we don't do as many encounters as the books push for," it would be useful (specifically and solely for advising people generally on ENWorld) to have another poll--"How many
encounters do you deal with between long rests?" By synthesizing those two pieces of information, we could figure out roughly what people are doing, at least within this tiny microcosm of the D&D world.
Still--it feels telling, to me, that people DO seem to think that six-ish encounters a day is a good baseline...and that around 1.5 rests per day is also a good baseline. While confirmation bias could clearly be applying here, and this poll doesn't tell us anything about anyone who didn't vote in it...well, this is pretty much exactly what I expected to see. People are generally favoring few short rests between long rests, which means classes that depend on short rests are probably getting a raw deal at a lot of ENWorlder tables. Will it be obvious? Will it
matter? I have no idea. But I do think that, IF this trend applies outside of ENWorld (which I DO believe, even if I have no real data to back it up), it will be one of the places where 5e could have done a better job addressing stuff.