>But the full versions of the sites are often horrible for mobile.
I've never found that to be the case. Or if I did, it was far less often than being annoyed with the lacking, scaled down, "horizontally enhanced" mobile layout.
As an example of a site that is not good at all on mobile I would cite this very one.
In portrait mode the text is way too small to read and zooming in results in text that goes over the edge. In horizontal mode the experience is a bit better but one still needs good eyes to read the comments. Luckily there are enough applications that mitigate the problem.
While it works, it is also a hack that very few people know how to use in general my guess would be less than 1%. This site being a huge exception, due to its nature. To scroll past a thread you can collapse it.
As more and more browsing happens on mobile, that should be the new default.
I've never found that to be the case. Or if I did, it was far less often than being annoyed with the lacking, scaled down, "horizontally enhanced" mobile layout.