My experience is as anecdotal as yours, but it seems to me that the typical conservative male is more likely to return the cart than not. Conservatives, as backward as they can be, typically have irrationally higher expectations for certain rules.

These are the same people who would be ok with police brutality, but would be upset with swearing in front of an old lady.

The people I see leaving carts more often than not are older people (perfectly capable of walking into, through, and out of the store but act like they're too frail to return the cart) or two different groups of women (stuck up Karens or moms who are by themselves with children).