Do you want to be the person who has to explain why your userbase just dropped 20% because you didn't want to ban porn? If Apple says you want to ban something, it's getting banned. "Globally" is also not a good metric here, since the vast majority of tumblr users came from english speaking countries.

In the local galactic supercluster it might be less than 0.1%, but Tumblr happens to be predominantly used in the US, and that's what matters to their business.

Nobody cares about that though. US is where all tech happens.

Weighted by ad revenue, it’s closer to 50%.

Yes, the 20% that has all the money.