Major League managing is a tough gig. You get blamed for things you have little control over, your every move is scrutinized and second guessed by people who've never so much as managed Little League, you work insane hours and travel incessantly, most of your supposed employees get paid more than you -- and even if you were as good at your job as you possibly could be, it likely would only make a few games' difference in the standings. It's not coal mining or anything, let's not get carried away, but it's no picnic. And the job security is notoriously lousy.
Of the 30 major league managers, nine are in the last year of their contracts. But how much does being a "lame duck" actually matter? The vast majority of manager salaries are low enough, by baseball standards, that it's not a huge impediment to firing them anyway -- as the recent fates of Ozzie Guillen and Bobby Valentine remind us.