Nature versus nurture. I don't think everyone has the same response to external stimuli or lack thereof. I would be hard pressed to nail down any one reason why I am the way I am - I mostly like to think of it as me just being me.
Having feelings is different than acting on them or having them control you.

I do think that some people find with continuing to see the therapist, their need for external validation reduces more naturally and it is not such a stark black and white line.