There seems to be 'trend' that's been forming over the past few years towards smaller and smaller flies.
Quite a few experienced fly anglers I know are reaching for the midge box as the 'go to' place to start on most of the streams they fish.
That new book, MODERN MIDGES (Takahashi) has hundreds of patterns in it, the vast majority in sizes 20 or smaller.
Makes sense that the thread makers would try to offer smaller diameter threads to fit this trend. I'm not sure that such fine theads are superior tools for this kind of tying, but that's a different discussion.
In a few years it will likely change again.
Buddy
It Just Doesn't Matter....