Can men also become only bald on their legs?
Hair loss is known as alopecia, and is often associated with hair loss on the head. This type of hair loss is most noticeable, but hair loss can occur in nearly any part of the body, including the legs (source: Healthline). As an anecdote - my father in law (65+) has lost all his hair on his legs. This hair loss is referred to as anterolateral leg alopecia

About 35 percent of older men have this condition. The exact causes of anterolateral leg alopecia are unknown, but there may be a genetic component.

Age related hair loss in men is referred to as male pattern baldness, or androgenic alopecia. This type is related to hormones and certain genes.