The democratic process incentivises transparency. You want to make public all the good work you're doing and the opposition wants to discover all the bad you did so they could turn the people against you in next elections. And it also does guarantee more rights (although eventually) as history has already proven.
But driving requires a person to be above a certain age. They have to go through a test to prove they're competent. And there's still certain rules to follow like not being intoxicated while driving even after they have proved themselves to be competent.
And most importantly driving is a privilege that can be taken away if someone repeatedly fails to comply with the rules. So not really a rational rationale