It makes a lot of sense, if we think about how the protocol works. Without caching, I assume every client would send every query in it's entirety to the root se

It makes a lot of sense, if we think about how the protocol works. Without caching, I assume every client would send every query in it's entirety to the root server, right? Since a single zone can have multiple labels ({abc.def}.ghi.example - abc.def is a NAME in ghi.example), the server needs to receive the entire requested name in order to properly respond (yeah, root queries usualy optimize this, because all NAMEs there are one label long).