I do want to be encumbered when the items I pick up are actually impactful. Inventory management in a game of limited resources should be essential. If I pick up a healing item that actually matters, I want it to have weight. I also hate generic stacking...

"You can have 9 of each potion type"...what if I want 16 of one potion type and 2 of another? "Nope". Weight systems inherently cater to a more diverse set of playstyles, given a system of limited resources, and you can't have a weight system without encumbrance.