That wouldn't work, because jQuery would have multiple versions in the wild, custom builds, forks, etc.. Not only would almost no one have a cache hit because o

That wouldn't work, because jQuery would have multiple versions in the wild, custom builds, forks, etc.. Not only would almost no one have a cache hit because of that, but every time a CDN is down or overloaded, your website is now artificially slow... or broken, which happens far more often than a cache hit.