To show contrast. For three years there was Palmer: good, solid, level-headed leader. Keeler appeared to be okay, too, for as long as he lasted. Now they're showing how dangerous an incompetent empty-suit president would be. IMO.
And even Palmer wasn't really great at the start, because he was feeling his way through a new crisis, not sure who to trust. By year two he knew who to trust.
It's more fun though knowing that just when Jack is ready to wrap things up, the CIC can force the agents to drag him back to CTU so the bad guys can get away. Last year he was ready to take our Marfan and they sent in an agent to force him out, tipping Marfan off to their presence.
Logan is a guy who is very insecure, so he never knows what to do and listens to one or two other people, usually the wrong person. He then deliberately goes against other people, to "prove" his manhood.