Originally Posted by
Pratt
Rowing favors a tall body type, not many elite cyclists are all that tall, are they?
Grand Tour riders and CG contenders tend to be quite short as power/weight ratio is a major factor, and it's difficult to be over 6' tall and under 65 kgs and still produce enough power to win bike races. You still get the likes of Froome, Hugh Carthy, the Schleck brothers being quite gangly and winning mountainous races, but most GC riders tend to be in the 5'8-5'10 range (Roglic, Pogacar).
Classics riders and sprinters, where the kg side of the W/kg balance is less important, can be a lot taller. Tom Boonen, Marcel Kittel, Fabian Cancellara, Niki Terpstra are all over 6'. But there isn't much penalty to being short (Caleb Ewan, Oscar Freire).
I knew a lot of rowers in college, the athletic requirement are similar. One difference is that there's no hiding in the wheels and saving your energy when you're in a boat. Another is that it's over in less than 10 minutes.