It's not just a Thunderbolt/ Mavericks feature.
You can do a similar thing over Firewire, it allows you to network 2 Macs when no ethernet or wifi was available. You would also get lightning fast transfers Mac to Mac over Firewire or Thunderbolt using IP networking. You can even daisychain via disks & hubs too !
If one Mac is on a real network (ethernet or wifi) with internet you can also share this via TB & internet sharing.
It's not something everyone needs, so you are right about deleting the option or drag it to the bottom of the 'Service order' list, but it is pretty neat if you need fast networking & only have a TB or Firewire cable.
The OS will try to fall back to any type of connection in the service list, so you should probably investigate why the other types of connection are dropping.