To be complete, the exact figures are estimates, but whether it's 300,000 or 600,000, no one disputes the number without Photo ID is very large. Every state that has estimated the number comes up with figures in the multi-hundred thousand registered voter range.
But to answer your irrelevant sociological question, many poor people don't have cars or drive. Poor people don't travel by air, and they sure as hell don't travel abroad. Many poor people don't have bank accounts. Many people rich or poor do not drink and so need no ID for alcohol. Or they get alcohol from the local store where the owner knows them and doesn't comply with the requirements to check ID.