Each of those connections needs its own TCP and TLS handshake making a total of 6 trips. Also, although this didn't take off, h2 had push promise which could have been a big help.
Yeah HTTP/2 push is so great that Chrome removed it.
Straight from the horse mouth: "However, it was problematic as Jake Archibald wrote about previously, and the performance benefits were often difficult to realize"
https://developer.chrome.com/blog/removing-push