The dragons got discouraged again from marrying humans when the hatred and dislike of humans did not fade over the years despite the fact that on their part, they had done their best to forgive the humans for almost wiping them out.
Dragons understood that the world was kill or be killed. It was survival of the fittest. Being the prey at that time only meant they became weak. Thus, they had to be strong again.
They also understood that they also had a fault which was why the humans' discontent and anger grew until they decided to wipe out the dragons and the long-lived races entirely.
They did not understand the plight of humans back then. But now, they do after observing the human race much more closely.
The long-lived races also understood that living separately from humans was so much better since their lifespans, indeed, differed too much.
