It doesn't. jquery-ujs will still be there if you want it, but depending on jquery brings along a lot of baggage along with the legacy browser support it allows

It doesn't. jquery-ujs will still be there if you want it, but depending on jquery brings along a lot of baggage along with the legacy browser support it allows. This discussion is just about what the default should be, and I don't think its unreasonable these days to aim for modern browsers as a default for most sites.