That's true, but then the people you're selling to have to want to buy the shares. And if you're buying YES at 97%, you're not going to be able to sell the YES shares to anyone at much higher - because eventually someone has to hold it to the end.
It's true that this isn't as true for NO, because a small change can give a huge return, but that's asymmetrical. So there's incentive for traders to buy NO, hoping that it moves down, but not an incentive for traders to buy YES, since it doesn't have any room to go up.