I am an intensive mobile user and sometimes I meed functionalities of the full page (desktop page). The "desktop site" of mobile Chrome and other browsers has long been ineffective. The only way is to click "full site" on the bottom-right of the page. To switch back, I have to find the "Mobile" link on the bttom-left and tap it. This is very inconvenient compared to just closing the tab, had the page respected my "request desktop site" option.
It used to respect that option and I used to have a better experience with using full site on mobile. Besides, SE chat seems to all working with that option. Then what's with Q/A site pages?