Apple has gone to great lengths to keep adult content out of the iOS store, from censoring comic books to banning apps that cross their guidelines. Steve Jobs even famously said "folks who want porn can buy an Android phone," but where there is a will there is a way, and thanks to the proliferation of streaming adult content there are a lot of ways.
According to data released by the online smut peddlers at Pornhub, Safari for iOS is used more than any other mobile phone browser for viewing the site. Safari for iOS accounts for 38% of mobile phone browser traffic, which is a big number but still within range of the 29.4% of traffic that Android browser makes up. Chrome meanwhile makes up 18%.
On tablets however, it's a not even remotely close. Safari for iOS makes up a staggering 73% of all tablet traffic to the adult website. Android's browser only makes up 7.8%, with Chrome taking 13.6%.
The moral of the story seems to be there's no way to truly stop the desires of the users of your technology. Jobs might have wanted iOS to be a pure space, but ultimately policing the app store can only achieve so much. Regardless, Steve Jobs would probably be disappointed with iPad users right about now.
If you'd like to read the report yourself, you can find it here. Please keep in mind that even if the blog itself is just data, the site itself is still very Not Safe For Work.