Question: Out of curiosity, why does it often take *seconds* to obtain network configuration via DHCP when the CPU is capable of processing millions of operations per second and ping to the router takes a couple of milliseconds?

In my home environment with one WiFi router and about 5 devices, it is not rare to see times like 5-10 seconds.

Answer: 
In addition to the actual acquisition of the DHCP lease from the DHCP server (which typically doesn't take very long), some servers will first ping the IP address it's about to hand out before it actually hands it out to verify that it's not already in use on the network - this takes a few seconds to time out. The client sometimes will do the same (again, to prevent IP address conflicts) which will add some more time. Then, on top of that, some clients will also register their DNS entries etc.
I don´t know what scenary you have, but in the real world you get the ip address...etc from an old server (dhcp server is always the one with the oldest hardware :) ) with lots of requests, behind a firewall, one or several routers/switches... Latency, cpu power...and in a windows world, dhcp implementation is not as efficient as we would like!.