lol why don't people check how much filament they have BEFORE starting a print ?
The slicer tells you how much you'll need. It's not rocket science :-)

These days I don't get snags or snaps - you just need to buy the right filament. Had a few when I was starting out.

Never run out of filament - 'cos i check before starting a print.

But there are going to be alot of people who don't take sensible precautions and if you've got a bunch of machines going, a sensor might be a good idea.