Simply not true (i've watched all 90 minutes of our games this season bar 2 games). I doubt you've watched more and the general consensus amongst spurs fans is he should play whenever he's fit.
I've watched quite a bit of Spurs, my friend's a huge fan and I've watched most games with him. We're obviously just seeing two different things. I'm not even saying Campbell is better, but King is certainly on the decline even when healthy.