I wonder if there's a functional reason why they do this, rather than just implementing responsive design / media queries? I seem to remember more sites doing this ~5 years ago, but based on what I see, it has fallen out of favour.

(Actually found some info if anyone is curious: https://medium.com/freely-sharing-the-sum-of-all-knowledge/w.... Though the article helps explain some of the context and reasoning, I don't think it really justifies the divergent experience and imperceptible progress on improving the desktop experience)