In my case, I've discovered that Devonthink (document/notes management app) is responsible. I've been meaning to file a bug report about it.
I'm surprised that Apple's power management doesn't have an alert for this. Surely an app that causes my Mac to become glowing hot while sitting in my backpack, not to mention slowly running out of battery, is a pretty important thing to intercept. Meanwhile, I keep being asked if Chrome should be allowed to find devices on my network, which doesn't seem nearly as important.
1. I had no idea you could do this, thanks.
2. Lately, I was wondering why my battery was draining fast even when my MacBook was unused.
3. Turns out, Firefox is preventing sleep. Something about videos auto-playing, apparently. Not great, but it can be fixed.