IMO a dropdown is pretty much a must when dabbing.
Keeps any wayward heat away from your main rig, and reclaim will condense there first, so your rig stays cleaner, and you get more dry reclaim and less wet reclaim
Getting into the habit of using dropdowns also means your nails can become a bit more versatile - no need for a multi-size nail or multiple nails, just grab a dropdown that has the right joints for your rig and nail
Also, IMO, a dirty dropdown will taint the taste of your dab less than an equivalently dirty rig...
I'm not sure if it's that wet-claim tastes different, or if it's just because it makes more contact with the water that the water picks up more dirty flavour, but I noticed my FC-710 needed fewer ISO rinses once I started using a dropdown.
None of those are really "function" in the strictest sense though...
More just enhancing the overall experience - If they do really annoy you, that annoyance probably outweighs most of their benefit (though I do think the heat thing is a pretty major plus for dropdowns)
EDIT:
Also, if you want to move your nail off your rig for some reason (either to use another rig with the nail, or another vape with the rig), a dropdown makes it way easier to do so without burning yourself