"Both of these libraries should be unnecessary and hopefully obsoleted by browsers someday. Browsers already implement techniques like this to process CSS styles efficiently. It's still unfortunate we have no native implementation of declarative event handlers, even though people have been doing this since 2006."

I think they believe jQuery will rapidly become the past so no reason to merge it.

"both" referring to selector-set and jquery patch. Its wishful thinking that browsers could expose a similar api as selector set that they already use for matching css rules.