... and unless you don't count situations where you ran away from an encounter you were losing, rested and healed, possibly acquired some new equipment specifically to deal with the enemy that forced you to run away, and then came back (which definitely happened a few times a year while I was playing 3.x), then that's just bizarre.
Bizarre to you, but judging from past responses, I'm not alone.
See, its not the retreating that makes it a 15 minute workday, its WHEN and HOW OFTEN you do it, and with what in the tank. Let's put it this way: nearly every time our party has rested, we still had resources available. Maybe not much; maybe my Cleric/Sorc was on the front line next to the Rogue because the dinged-up fighter was too fragile to do anything but shoot his bow. But when we rest, it's not after 3-4 combats, it's 5-8.
Part of the secret is to
always try to hold something in reserve. In 3.X, our spellcasters don't lob spells when the situation is well in hand. That playstyle let us get through 7 encounters in RttToEE with the party's Wizard still having at least 2 6th level spells left. My 4Ed Starlock (MC: Psion) hasn't used a Daily power in the last 3 sessions (covering 2 campaign days)...and hasn't dipped below half of his available Healing Surges despite getting involved in
melee 2 times in those sessions.
And this isn't an isolated thing: my 34 years in the hobby has been spent in 5 cities in 3 states and with 10 different groups.* No 15 minute workday.
So, while it's only anecdotal, it seems to be a lot more common than you seem to think it is.
* and covering 90+ systems- though each group played some form of D&D but one.