What gives is that just because YOU are capable of transferring at 30Mbps, it doesn't mean that whoever is sending you the file (be it a server, seed, any other cdn...) can handle 30MBps. Also if it helps, imagine the internet as a vast system of pipes, some wider and some thinner. The path between you and whoever is sending the files might go through some thinner pipes and lose some of the speed, per se.