People could rationally decide that prolonged relationships take up too much time and effort and that they'd much rather do other kinds of things. But most people are afraid of rejection.
I was told to avoid the business all together because of the rejection. People would say to me 'Don't you want to have a normal job and a normal family?' I guess that would be good advice for some people but I wanted to act.
The radical novelty of modern science lies precisely in the rejection of the belief that the forces which move the stars and atoms are contingent upon the preferences of the human heart.