It took me a long time to learn to stand. I couldn't even do it on a spin bike at the gym!
Now that I can do it, I rarely do. It hurts my knees and since I have no trouble getting up most grades up to 15% or so, I would rather sit and spin in the granniest of granny. I might have wanted to stand on the two 20+% grades that have defeated me, but at that point, I couldn't move, let alone stand!