Robbo's useful - he's a pack marking, goal kicking, sometime match-winning forward - that's why he's got trade value. I don't think you'll see too many articles where clubs are chasing players who are useless.
But he's 29, has a bung knee and is not a team player.
Yze and Bizzell illustrate the risks of giving players in this situation 3 years, we're absolutely right sticking with 2 years or trade him if we benefit.