What's with tape on the nipples?

just think of them as mannequin nips.

because it is not considered nudity (topless) unless the nips are showing and by not having a nip showing it is less likely to be spread across the internet and such.

The rules about what you're allowed to do on set are different depending on the jurisdiction (state, country), and you also have to think about the ratings rules for where you hope the movie will sell. And also, if the stars don't want to show skin, you need a Nipple Extra or peculiar camera angles etc.

It comes down to money in most cases, and filmmakers will tend to go for what costs less. But I have a feeling that in Fiji (strong moslem population) filmmaking showing nipples was probably forbidden.

In some jurisdictions in the USA, saran wrap is considered to be clothing when it comes to movie making, so you see the players getting some very thin, very transparent sticky plastic wrap applied to themselves before a take. It's so transparent and it sticks on so well they look completely naked, but if a censor or local authority asks it's "Don't worry sir, they were completely clothed at all times".



WARNING!
Objects under T-shirt are larger than they appear!