> it's not hard to create a simple UX that would enable this.
This is a gross understatement. The number of different clients that Twitter supports (apis, third party clients/vendors, mobile, etc) means that it isn't a simple problem. Not only that but they have to support different screen sizes and likely have to crop the image differently depending on the device you're viewing the content on. I can without much mental effort understand how this feature comes to be. People spend more time looking at pictures that are interesting and in order to support all of the different screen sizes they decided it was easier for their users to attempt to automatically frame the image.
Sure but as I mentioned in my original comment you're assuming that Tweets are only created in a Twitter owned property and this just isn't the case at all. I have no insider knowledge here but my hunch is when they were talking about this problem the calculus was "Do we just make photos posted from the Twitter web or mobile client look good or maybe we can use some ML to attempt to make photos from anywhere look good". I am not at all advocating whether they are doing a good job at that or not but reducing the problem to "a simple UX to select a focal point" is ignoring the massive surface of the problem.
I'd argue that "maybe we can use some ML to attempt to make photos from anywhere look good" is also ignoring the massive surface of the problem, with predictably bad results.
They are both large problems which is my point but given the choice between two hard problems I can understand why they chose the one that has the potential to solve the entire surface instead of just part of it.
So what you're saying is, it's easier to create a magical AI that can decide with 100% confidence the best visual area of the photo, than a UI component?
This is a gross understatement. The number of different clients that Twitter supports (apis, third party clients/vendors, mobile, etc) means that it isn't a simple problem. Not only that but they have to support different screen sizes and likely have to crop the image differently depending on the device you're viewing the content on. I can without much mental effort understand how this feature comes to be. People spend more time looking at pictures that are interesting and in order to support all of the different screen sizes they decided it was easier for their users to attempt to automatically frame the image.