...but multiple TCP connections (within reason: too many causes a problem, but not just a handful) actually almost always out-perform a single one for numerous

...but multiple TCP connections (within reason: too many causes a problem, but not just a handful) actually almost always out-perform a single one for numerous reasons (including the congestion controller having more leverage from looking like multiple users, being able to hit multiple backend machines from dns load balancing, and working around various per-connection bottlenecks); this is in fact the primary trick of "download helpers": they download multiple independent segments of the file on parallel connections.