Legacy reasons. When the iPhone came out, "mobile only" sites were a wasteland of terrible UI and restricted features. iPhone OS wanted to serve full websites,

Legacy reasons. When the iPhone came out, "mobile only" sites were a wasteland of terrible UI and restricted features. iPhone OS wanted to serve full websites, and sometimes had to do weird things to beat the kind of stuff that sniffed for mobile devices, or to overcome the lack of a mouse on a desktop website. If you look at the original iPhone demo in 2007[0], the original intent was to render full web pages on the screen and rely on the double-tap-to-zoom to read content. The article that's generally credited with naming and mainstreaming Responsive Web Design[1] didn't come until 2010. [0]: https://youtu.be/vN4U5FqrOdQ?t=2502 https://youtu.be/vN4U5FqrOdQ?t=2502 [1]: https://alistapart.com/article/responsive-web-design/ https://alistapart.com/article/responsive-web-design/