- . . . because it's a challenge, and because I think seated pedaling more specific training for climbing up steep hills on skis (classic) in the backcountry.
Why does standing work better for the steepest climbs on asphalt?
High hips -- that's my new theory. Standing on a bicycle is like skating up a hill with high hips. Seated pedaling is like skating with my "butt down in the bucket".
High hips works better for high-force situations just by trigonometry: smaller knee-bend angle means that the same propulsive force to the ground can be delivered from lower tension force in the upper leg muscles.
- I think swinging the frame of a (road) bike from side to side while climbing (or sprinting) makes it possible to focus the range-of-motion even more on less knee-bend angle.
Maybe it's why I spend all almost all my time seated pedaling up steep hills -- I somehow just like the feeling.
Key difference is that in bicycling it's easier to measure to find out which situations work better with high hips and less knee bend.