Originally Posted by neuron
also agree with the sentiment noumena9's got about the roadies spinning 5mph up hills... is that just to build CV?
Could be many reasons.
They are training within a target HR zone and don't want to go over it.
They are big bodied and are just better on the flats (*rouleurs*).
They like the functionality of their knees and would like to keep that functionality till their old age.
They are not interested in riding at race pace during a recovery ride.
Maybe they are going slower to enjoy the scenery.