Maybe I should define the need is for commuting, endurance cycling, touring or anything like TDF but NOT for short distanced racing. I believe many people can go like a rocket in maybe 1 or 2 miles
The difference between a Tour de France champion and a non pro is more on the hills:
http://www.bicycling.com/2011-tour-de-france/you-versus-peloton
Many people can go higher than 25 mph on flat or down hills but for how long before you have to climb a hill? The difference between a TDF champion and a non pro on flat is actually not that big. Even you run out of gears on a 39 front ring on flat or descent it won't affect your avg as much as you climb a hill where you will use a 39 ring anyway. What I am saying is 50 ish ring is something nice to have but one can totally get by with a 39 T ring (again not for short distanced racing). Plus one saves a little bit of weight and maintenance.
The difference between a Tour de France champion and a non pro is more on the hills:
http://www.bicycling.com/2011-tour-de-france/you-versus-peloton
Many people can go higher than 25 mph on flat or down hills but for how long before you have to climb a hill? The difference between a TDF champion and a non pro on flat is actually not that big. Even you run out of gears on a 39 front ring on flat or descent it won't affect your avg as much as you climb a hill where you will use a 39 ring anyway. What I am saying is 50 ish ring is something nice to have but one can totally get by with a 39 T ring (again not for short distanced racing). Plus one saves a little bit of weight and maintenance.