ok, well if you dont mind telling me, why is this all "preposterous"? Why would you to NOT ride dragons?
Well in the TES universe and many other fantasy lore dragons are considered very intelligent and mystical beings. Most of them being a sentient creature would find it insulting to have a mere human or some ofter bipedal riding piggy back on them like some kind of mule, pet, slave.
They have their own agendas and don't want to be running around as some lowly creature's mount and carrying all his stuff like a pack mule.
How woud you feel if someone put a saddle on you and told you to go somewhere with all this crap on your back without your consent? While you were very much larger than him, can breathe fire, and fly?