WWE departures

Scott, after hearing Heyman last night and being a younger fan, why exactly did Brock leave WWE the first time?  I always thought he was just fickle and sick of the travel schedule but was there anything to him "being sick of the politics" as Heyman alluded to?  This also got me to thinking…why exactly did Stone Cold leave WWE so many times?  My assumption was it was always due to injuries but people always mention him "taking his ball" and going home.  Did injuries really cause him to walk away numerous times or is there more to it?  Thanks MH

Brock left the first time because, as you noted, he was sick of the travel and Vince wouldn't capitulate to his every little demand.  The contract dispute stuff was pretty inside, actually.  
Austin left so many times because he has no financial incentive to put up with the bullshit surrounding him and can basically come and go at his own whim.  He worked injured for his entire career more or less, so it wasn't really injuries until the final back injury ended his career in 2003.  Other than that it was mostly just the writers coming up with incredibly stupid stuff for him to be doing (like jobbing to the Coach) and Austin telling WWE to fuck off.  I don't think it was ever personal when he did it, he would just disagree with creative frequently and didn't want to bother any longer.  And hey, the dude makes millions of dollars off merchandise and residuals, so he's got every right to hold out for storylines that aren't incredibly dumb.