One of the primary features of HTTP/2 is that it makes use of multiplexing, so that many logical streams are sent over the same physical TCP connection. This makes a lot of things better and faster. It makes congestion control work much better, it lets users use TCP much better and thus properly saturate the bandwidth, makes the TCP connections more long-lived - which is good so that they get up to full speed more frequently than before. Header compression makes it use less bandwidth.