It's a poll tax. How we've let it become the norm is beyond me, but it prevents millions of people from voting every year.
Are you ensuring that people can get them with no hassle? Voting is the most fundamental right in a Democracy, any barrier to voting is a problem as far as the Constitution is concerned. Any undue burden is a problem. Sworn affidavits have worked for decades and will continue to work.
Voter ID is a solution to a problem that doesn't exist at all. And it disenfranchises millions.
The ID itself might be free. But if it requires government documents such as birth or marriage certificates it is not free. It is an added cost for women that marry or have multiple marriages.
There may be additional court costs to correct mistakes with birth records. If my dad were alive he might have difficulty due to the fact someone other than his parents informed the person what he was named. They indicated Junior as his middle name instead of the correct name.
When it also involves getting documents in another state you are also dealing with mailing costs and or transporation.
What a way to overcome the opposition - make sure there are far fewer of them.
Compulsory voting, combined with a majority rules system that eliminates the Electoral College, gerrymandering, and other provisions that alter the power of your vote based upon where you live, might be the best answer.