Thank you for writing this. I am turning it over. I wonder how we can teach this to players, aside from devising systems which incentivize using items, such as by the use of temporary use-it-or-lose-it items , or by the capacity to transform items into other benefits in a timely fashion. Some games, such as the oft-lauded "inventory Tetris", do teach players to think of inventory as a skill. Aside from including puzzle mechanics such as that which can make the player feel challenged rather than restricted, I think that, inevitably, asking players to fight against arbitrary limits will produce negative frustration.
Envision an inventory system where one can collect infinite amounts of items in safe chests but only carry a limited quantity or weight with them. Players tend to like these better. Restricting inventory often simply leads to players ignoring vast aspects of gameplay entirely because they do not want to carry items with limited uses. Even in a game such as Sekiro (in which one can grind infinite spirit emblems and can only carry a small amount), many players opt to not use their spirit emblems at all due to a concern of eventually running out, while a renewable resource such as Estus flasks in Dark Souls (in which the flasks refill endlessly at any safe zone, with no grinding required) does not lend itself to low usage.
I see players hoarding items they will never use or touch. I would like to think of ways to incentivize players using items and actually engaging with all game systems.