Step 1. Go to the DMG where it gives the encounter building guidelines.
Step 2. Actually read those guidelines.
Step 3. Realize that 3 deadly encounters per day or 5 hard encounters per day are within these guidelines.
Step 4. Realize that 6-8 encounters per day is a myth
Easy and medium difficulty encounters are both so trivially easy that any party with half a brain will completely steamroll them. For the most part, I don't find that fun. As a player, I want encounters to be challenging where the outcome isn't entirely certain. As a DM, I don't want to waste time designing an encounter whose sole purpose is to chip away at party resources. If there is an encounter, I want it to be meaningful.
Page 58 from the Basic DMG:
"...most adventuring parties can handle about six to eight medium or hard encounters in a day."
But most importantly, the point I'm trying to make is that if you are playing in a style different from the expectation of the rules, you need to understand that's
you making changes, and you can't fault the game because you're deviating from said expected playstyle*. Most of us do it. I certainly have houserules. For example, it also clearly states (and is common sense) that even easy or medium encounters will take away some party resources. Especially if you have a DM that doesn't run the monsters as mindless bags of hit points but runs them like they would probably normally act** If you just skip all of those and give the PCs an auto-win with no loss of resources, your houserule is stacking the cards in the benefit of the PCs, especially those who have limited big-shot abilities.
*the expected play is most certainly not one of "just skip all easy and medium encounters."
** for example, I have several encounters with kobolds when the party is around level 4-5 when they meet them. But the kobolds do a bunch of hit and run ambush tactics, liberal use of traps and environment, and tactics that have made those "technically very easy encounters from an XP budget rule" into fairly challenging ones in actual play.
I also disagree with your assumption that an encounter has to be hard to be meaningful. This an RPG, not arena combat. THere's lots of things that go into making an encounter meaningful beyond how many HP are lost on both sides. Are enemies made? Did opponents flee and alert others? Did you capture and interrogate an enemy for info? The list is nearly endless