Rather than address this tangent, let's just go to the DMG.
Your claim that "According to the rules, the point of the 6-8 encounters day is to diminish resources" is false. In a sense you have it exactly backward. The point of the 6-8 encounters is to give the DM a guideline on how many encounters a typical party will likely be able to get through in day. It's right on page 84:
"Assuming typical adventuring conditions and average luck, most adventuring parties can handle about six to eight medium or hard encounters in a day. If the adventure has more easy encounters, the adventurers can get through more. If it has more deadly encounters, they can handle fewer. In the same way you figure out the difficulty of an encounter, you can use the XP values of monsters and other opponents in an adventure as a guideline for how far the party is likely to progress."
Which all means that 6-8 encounters is in no way a "rule" of the game, it's a guideline that the designers used when designing the rules. The text specifies that there can be more encounters, or fewer. Encounters were not designed to drain a certain amount of character resources, character resources were designed with the goal of 6-8 typical encounters being the baseline. According to the rules.
But more importantly, we now go to page 85, where "the rules" state that "Some players and DMs view random encounters in an adventure as time-wasters, yet well-designed random encounters can serve a variety of useful purposes." It then does indeed list drain character resources...as the third of six useful purposes. The others are create urgency, establish atmosphere, provide assistance, add interest, and reinforce campaign themes.
As such, "according to the rules", draining character resources is only one of six possible purposes for an encounter. So the claim that according to the rules, encounters are there to drain character resources is blatantly false. According to the rules, an encounter that serves only to reinforce campaign themes (and not drain resources), is still a useful encounter.