This is something I've been thinking about as a DM in my encounter design: Why have easy/medium/etc combat encounters that don't really require resources to successfully complete?

Given the limited time many of our tables have to actually play, I've never created "easy" combats that don't require resources because they seem like a waste of table time. If there isn't a challenge and no resources are needed to overcome the enemy, then isn't the combat win just kind of a gimme and it's only actual resource used is everyone's actual time at the table?

I've generally looked at 5e combat like a game of resources and in order to successfully challenge my players to make it interesting, the combat generally has to be difficult - but I'm wondering if there's something I'm missing to the easy-win combats.