This leaves the teir 1 and 2 support staffs in a crappy condition. The only people worth keeping are the ones jumping at the first chance to get out of the 'helpdesk' role. So the IT deparment is left with their only real interface to the rest of the company being comprised of (often) barely adequate people. An individual's experience when contacting the IT department litteraly depends on who answers the phone; will it be a person from the first, second, or third group as mentioned above?
Hopefully the trend will change in the future, but it's probably going to require higher pay while allowing those people to also do more advanced things to keep them challenged/happy (that still may not be enough, because to be honest we don't like dealing with the regular day to day helpdesk-style problems anymore than anyone else in the company likes having them). Large companies are just too compartmentalized to do that, so we may all be doomed :(