The only real use I've found for them is that they prevent the clip from getting snagged/broken off if you're pulling the cable out of a big pile of other cables. Other than that, they just get in the way and block LED's on some devices.
If I dont leave them off cables I make, I put them on but pull them back off the connector so they're hanging on the cable. This way if I need to pull the cable out, I can always slide the boot up so the clip wont break off while I'm pulling the cable out.