I think part of it has to do with what is designated a jamming song and what is not. After so many 'in the box' Boogie On's in 3.0, it's probably hard to get everyone together for an extended jam. I especially thought this was the case in the Roses where the song portion had ended and it was like how do we keep this going? In past eras they go back to their signature sound for that era like the funky interlude after the song in Island Roses (if memory serves correct). That kind of platform would then be the bridge to an extended jam. But now there's no go to style so it seems more difficult, you need an idea for the jam's direction almost immediately. I think that's also the reason why Mike's suffers the same fate. After the closing chords that's pretty much it. One could argue the jams are overall more original in 3.0 because of this lack of style but it also seems to bar the door to extended jamming quite often.