Cynics are hard to disappoint. Because they imagine the worst in people and situations, reality rarely lets them down. Cynicism is a way to rehearse the let-downs the world has in store–before they arrive.
And the cynic chooses this attitude at the expense of the group. Because he can't bear to be disappointed, he shares his rehearsed disappointment with the rest of us, slowing down projects, betting on lousy outcomes and dampening enthusiasm.
Someone betting on the worst outcomes is going to be correct now and then, but that doesn't mean we need to have him on our team. I'd rather work with people brave enough to embrace possible futures at the expense of being disappointed now and then.
Don't expect kudos or respect for being a cynic. It's selfish.