Why do registered voters end up not voting?

[satsuma]

Yes, I think just in general, there's a lot of apathy or dislike of all involved.

People who often move may have some difficulty keeping up with the paperwork involved or not even be "on paper" living in the place where they actually are.

And yeah if you're counting the voter registrations people leave behind when they leave the state, that could count the frequent movers as being registered in more than 1 state.

Motor voter exists in every state, essentially: 6 are exempt because they "have no voter registration requirement or have continually offered Election Day registration since Aug. 1, 1994." Most blue states (and a few red/purple) now go beyond the requirements of the Clinton bill by registering driver's license applicants automatically, rather than as an option.

Personal experience: I got my driver's license at 16 and there were voter registration drives at my high school so I could register at 17 (but not vote until 18). When I moved in my early 20s, I skipped one presidential election in part due to being disillusioned, but when I eventually bothered to get my new driver's license I opted to register to vote and then started voting in my new state.