Voter ID. Why are some afraid of it and won't vote in person?

Voter ID. Why are some afraid of it and won't vote in person? What's the big deal? What's there to hide? Why won't some show up in person? Finally what are some hiding? Hiding the fact that the easiest way to cheat  is mass mail in ballots.

Voting by mail should only be for those who are physically unable to get to the polls or those out of town on election day. What are your thoughts?