Some commentary from Zack Bloom on the Cloudflare Blog, looking at requests to CDNJS for versions of jQuery.
What we don’t see is a decline in our old versions which come close to the volume of growth of new versions when they’re released. In fact the release of 3.4.1, as popular as it quickly becomes, doesn’t change the trend of old version deprecation at all.
Sorta makes sense. We make CDNJS easy to use at CodePen, where people can quickly search for, find, and add libraries like jQuery to Pens. I very much doubt most users are rushing back to their old Pens to update versions when a new jQuery comes out.
And upgrading versions is hard and scary on large sites. I saw an Instagram from someone at Etsy (the photo is private) commemorating their upcoming upgrade off of jQuery 1.8.2, which is eight years old!