Why do I need mDNSResponder/howl?

[Dave]

Yet another one. I thought only microsoft installed network services 
willy-nilly without any regard for whether they're needed. 

'Howl is a cross-platform port of Apple's "Rendezvous" (multicast DNS)
service discovery and IP autoconfiguration.'

So ... when was I asked if I even needed/wanted this? How many people actually 
use it? Why does it default to being activated?