Because most guys wear shit until it falls apart and only have a few pairs. You have sneakers, boots, and dress shoes. Maybe sandals. What more do you need?

Women have a bunch, so the wear and tear is spread around. You also won't see a guy get rid of a shoe because it's slightly damaged or because he simply doesn't like it anymore.

The only reason you're probably seeing men's shoes at a thrift store is because the owner has died.