As a bona fide tomboy I speculate that Subaru does not appriciate the concept of a sock, much less a shoe.
There should be few exceptions in which she'd imprison her feet and deprive herself of the freedom to walk barefoot upon nature. However her main vice would thusly be that she'd walk barefoot upon cement or gravel, resulting in hard, leathery soles, which is not befitting an idol.
In such dire circumstances I volunteer myself as a custodian of her feet. By oath I will keep her skin moist, callous-free and most importantly thoroughly massaged and relaxed, so she may enjoy life in maximal comfort.
