Lots of people who were born in this country don't have birth certificates, and can't now get them. Through into the 1960's, lots of births in rural South Carolina (and particularly, obviously, among African-Americans) happened at home, with a midwife or other informal assistance, and either their births were not registered, or they were registered incorrectly. There are legal provisions for allowing those who don't have a birth certificate to get photo ID, but those provisions are themselves difficult to satisfy. See the article below, originally from Columbia, SC's
The State newspaper:
http://www.jackandjillpolitics.com/2011/07/journal-of-voter-suppression-2012-south-carolina-edition/I'm not going to estimate numbers here, or the potential effect on voter turnout. But it bears repeating that not everyone without photo ID in this country is in that situation just because they're lazy.