Mobile is one of them, although OP's arguments are valid as well. (http://conferences.sigcomm.org/co-next/2013/program/p303.pdf) Also, among many other things: every thing over SSL. Single Connection. Also, less of a technical problem, but as many already mentioned, too complicated as compared to plain text human readable HTTP 1.x

also ssl everywhere without authentication by default. ie slower, encrypted, but not actually safe.