I like having high gears on a bike, along with the regular gears.
Occasionally you may see storm clouds coming your way. It is nice to flick it up a few gears and do a sprint to a place where you can get out of the rain.
I sometimes like to pedal at high speed going down hill, particularly if, it is followed by an up hill section. If you gain a lot of speed going down hill, you can get a long way up the hill without excessive effort.
Even when just approaching a hill. I like to get up to a high speed, which likewise makes it easy to get a long way up the hill without excessive effort.