Don't know about 5E but 3.5 at least allowed a fresh corpse to be brought to a cleric and revived for a fee, if your own party had no means of True Resurrection. The DM could always be a dick and claim they don't want to come back, I guess. But if they are truly important to the campaign, surely that would be counter productive.

Literally the Dusties in Sigil. They're basically just necromancers who are also lawyers and loan sharks. They have contracts for their zombies. You sell your body when you're alive, they pay you, you eventually die and now you're a janitor at the local tavern for all eternity. They might even use those dudes who talk in rebuses as a PowerPoint to make the sale.

Meme is more about looting but hear me out:

I wish more fantasy RPGs used their own player conveniences as more than just player conveniences. Like, FF7's big "what the hell" moment when you can't just use a Phoenix Down on Aerith.

Dragon's Dogma has spoiled me on this. You can revive any fallen named NPC if you have a wake stone. They even get put in a special room for you to visit if you forget their body long enough, so you can never lose a vital NPC while still having chaotic, emergent action with monsters rampaging through town.

I cast...

TESTICULAR TORSION!

Sounds like Drunk History which I've always said would be better if it used muppets.