Administrative contacts for a domain amount to nothing more than a pre-confirmed spam address. Why the hell would anyone use an address where they actually have to suffer through reading the crap that comes in?
My personal domains have my correct contact info on - email, snail-mail and mobile. I occasionally get stuff like the definitely-not-a-renewal notices from the Domain Registry of America and friends, but it's noise in amongst the general spam and junk-mail I have to filter anyway.
More to the point, it's the Right Thing to do, because the *privilege* of occupying a chunk of Internet resource comes with the *responsibility* of being contactable if bad things are emanating from it. Then again, my oldest registration dates to when you still had to write a justification to a human as to why you should be granted a domain, and wait a few days for a response. (I suspect in the twilight years when this was a rubber-stamping exercise, but you *did* still have to write it.)