I think it all comes down to what Armstrong, a good-natured guy by all accounts and someone who knows how to get along in a room, said about Kessel:
http://www.sportsnet.ca/590/prime-time-sports/how-do-teammates-perceive-phil-kessel/
Kessel's a helluva talent. But he's not a leader type, he's not good with the media, and he's not a guy to do dirty work in the trenches when the going gets tough.
Generally speaking, a lot of that stuff is reasonably expected of a guy getting franchise money. Pittsburgh might be the one place where Kessel can get by without the burden of those expectations.
We saw firsthand the criticism that a guy like Neal got for not battling in the trenches like this board wanted, despite being a sniper who regularly produced at a 40 goal and 80 point pace, and he was making 3 mil less per than Kessel. He didn't create on his own like Kessel, but I think the same reasoning applies.