User blog comment:TheBlueRogue/Turn Your Favorite Character Into a Cyborg in the Deus Ex "Aug Pride" Event/@comment-28124725-20160804020607/@comment-25059466-20160806195934

In the comics, Tony actually makes Cap an energy shield, but Cap sticks to the classic shield because all you have to do is damage the bracer that projects the shield, and something along the lines of "The more parts there are, the easier it is to break."

Also, Cap only has to worry about his shield getting destroyed when he's up against apocalypse-level bad guys, because his shield is all but indestructible. In the comics, it can stand up to a cruise missile.