I won't speak for the awards & decoration ceremonies for the other branches of the service. In the Air Force such a ceremony can involve up to 15 people. Fiddling around with a sharp pin through an individual's dress uniform means someone at sometime during the ceremony is going to get stuck. There is also the possibility (haven't heard of it, but possible) of someone accusing the presenting officer of "groping". With the badge clip the ceremony moves along at pretty good speed, not to diminish the significance of the award/decoration.
Reasonable.
Then they could go full ‘blood-wings’, but that would probably cause other issues :)