As the current stories go, although official word of course does not confirm it:
Tumblr is only the disc one villain in this story. The final boss is the ghost of Steve JobsThe one thing I oddly have yet to mention in either of my lengthy missives about my ill-fated love of the Windows Phone OS, was the fact that like half the reason I'm here in the first place is becaues I'll be dead before I'll own a bloody Iphone. It's a long and very petty story, but suffice it to say that my bitter annoyance with Apple naturally grew into a keen interest in criticism of Apple. The criticism of Apple that existed a decade ago was mainly concerned with its
Walled Garden politics.
Quickly summarised: A walled garden is platform where the content available is curated by the people running it - in the specific case of the Iphone, the fact that the only software you're allowed to install on your device is software that follows the guidelines of the IOS app store.
With the way the internet and the usage of computers has evolved the last decade and half, it's hardly surprising that walled gardens are par for the course of the everyman. Most people I know use the internet mainly for social media and media consumption, all of which happen either on apps or on proprietary websites. The generation before me learned to use computers in order to use spreadsheets and text editing at work; the generation after are the digital natives who cannot imagine a world without youtube.
But nineties kids were young when the internet was young.
I entered fandom when the web was still the open sea that required some fundamental tech knowledge to be navigated, but which was gloriously anarchic and gloriously
equal when you learned how to make and share your websites. Even the fandom hubs were non-profit and run by amateurs. My computer was a tool, and the idea that the people manufacturing the tool was going to tell me what I was allowed to use it for was ridiculous. Even if my childish boicott of Iproducts wasn't a thing, I'd still be uncomfortable, to say the least, about using a platform that effectively wanted to dictate how I was using it. (ironically, the Windows store too is a Walled Garden. Let's talk about my hypocricy later)
But fandom, for all that it was full of early adopters in 2001, found its home in the proto-social media on LJ, and when it migrated from LJ, it didn't go to the known fandom-friendly LJ clones, but to modern social media. Finding out why people went to tumblr instead of dreamdwidth is nigh impossible at this point; whichever came first, fact is that the migration from LJ coincided with the smartphones taking over the mobile market. The result: A considerable amount of fandom is happening on phones, not computers. Phones use apps, and the stats say that about half of those apps will be curated by the IOS app store.
And the Apple business model is to be accessible to all users, and to be accessible to all users there needs to be handholding and protecting of the children, so ix-nay on the porn.
There is a debate going on about the World Wide Web vs. the app-based internet usage that I sadly have not followed nearly close enough to say something insightful about, but the tumblr strikethrough is the point where it hits fandom. Because
if tumblr is purging the smut becaues it lost half its mobile users, then there is a lot to be said about how Apple's policy makers are effectively no-platforming creators on third-party software, and policing the content consumption of their own customers. Ideally, you could say that this is of course the choice the IOS users make when they buy an Idevice, but if Apple is using their size to dictate the content on a third-party platform, then the internet just got a great bit worse than I used to think that it was.
I might never have been a particularly avid fan of tumblr, but dear god, if there ever was a reason for arguing that the move from the web to app-based internet was Bad News, it is if the policymakers of some multinational company is going to decide what kind of pictures I get to look at on a website which they do not even own.
ETA 15/12: The latest story going around is that tumblr was planning the porn bann already in August or September, though I can't find this confirmed anywhere. If it's true, it disproves the causality I speculate about here. Though not, I'm afraid, the theory behind it.