Instagram has finally unveiled the key reason why its users can't #freethenipple. It is pointing its finger at Apple.

Kevyn Systrom, CEO of the Facebook-owned company Instagram, spelled out the reason the app censors several photos of female nipples in an event organized by Dazed Media in Shoreditch, London.

Systrom went to say that Apple's App Store, which hosts Instagram, has stringent rules, saying if the app goes against these set policies, it could possibly lead to the removal of the app from the store.

Quite a few super stars, including Miley Cyrus, Chelsea Handler, Rihanna, Naomi Campbell and Chelsea Handler, helped the #freethenipple movement take off on Instagram, leading them to even post topless photos of themselves only to be taken down by Instagram administrators.

Systrom did say that the app store is just permitting explicit nudity if the app is rated 17+. To date, Instagram is rated 12+.

The chief executive did argue that if Instagram is to increase the age bracket, it would forbid younger users who are not actually enthusiastic about nudity.

Despite taking down #freethenipple efforts, the company claimed it is still devoted to artistic freedom. Systrom admitted, however, that "in order to scale effectively, there are [some] tough calls," including prohibiting of female nipples within the platform.

It is important to note, though, that the app's controversial community guidelines allow post-mastectomy scarring as well as photos of women breastfeeding.

In the meantime, when asked questions about the rise of Snapchat, Systrom seemed unconcerned. At present, celebrities are already signing up for a Snapchat account, which, as reports point out, may potentially take away content from Instagram.

Not too long ago, Naomi Campbell attempted to post her #freethenipple photo. It was then removed by Instagram after 20 hours. Chelsea Handler's photo, on the other hand, was censored after 30 minutes from the moment it was uploaded.

However, a report challenges rating claims of Systrom, mentioning Twitter, which is rated 4+, as an example. It says, Twitter presently houses porn accounts posting a wide array of photos and videos of nudity. Yet, Apple has not "brought down the hammer" on the platform.