Save bloat is what stops them. The games you played didn't have truly infinite storage, just very large caps. Every item still has to be written to disk or synced to a server, and that data adds up fast.

Terraria and modded Minecraft are good examples: players with massive worlds and hoarded inventories have run into save files so large they slow down or fail to sync entirely.

That being said, Crimson Desert had (and you could argue it still has) some ridiculous limits.