As an example of a possible use: I know that my Asus router shows vendor info on its page that displays DHCP leases. It seems like it's mostly based on the MAC vendor ID. I haven't ever examined where it gets that information from.

From real world experience, "I see this device getting an address from DHCP but I have no idea what our where it is and there aren't any useful ports or it's off right now. Is the MAC from a manufacturer I recognize?"

~5k requests per minute doesn't seem that much if it's just light processing and a map lookup. You can do a lot with a $10/m VPS.

I'd use it to trace computers on my network.