It is apparently common when they make movies and TV shows, that if a woman's nipples are showing too clearly through a shirt, they will tape them down!
Isn't that amazing? Here is a free gift of great sexiness, without nudity, and they remove it!
I can only guess that some parts of the general audience are so sexophobic that even the outline of nipples through a shirt (not even a transparent one, mind you) is so strongly offensive that the movie- or TV-outlet will get in trouble for it. Hokey mama.