D&D 5E Why are vehicle speeds so slow in the DMG?

[robus]

Stormwrack for 3.5 had a reasonable list of ship speeds...

Barge 1/2 mph
Caravel 3mph*
Cog 2 mph*
Coracle 1mph
Dhow 2mph
Dromond 2mph* or 3mph
Dugout 1mph
Elf wingship 4mph*
Galley 1-1/2mph* or 2mph
Greatship 2-1/2mph*
Ironclad 1mph* or 1mph
Junk 1-1/2mph*
Keelboat 1mph* or 1 mph
Launch 1-1/2 mph
Longship 1-1/2 mph* or 2mph
Pinnace 3mph* or 1/2mph
Raft 1/2mph
Rowboat 1mph
Theurgeme 3-1/2mph
Trireme 1-1/2mph* or 2mph
War canoe 1mph* or 2mph

(*base sailing speed in light winds)

Sailing speeds obviously vary depending on the wind speed, as indicated by the asterix. And some vessels can rely on sails as well as rowing.

That's cool but still too low IMHO.

This is some interesting reading: http://www.boats.com/reviews/crunching-numbers-hull-speed-boat-length/#.Wa1tIDO-Ic0

I know I'm way overthinking this....