See i still get this even though i'm more eNTP now. I'm sure its because anyone who knows me at all knows that they can tell me anything and i won't react with judgement i'll more just sort of interogate them slightly to figure out how there thinking so i can see it from their view then sort of point out where and why other people think differently which a lot of my friends value.
I think its because INTPs are such detached big picture thinkers so they are very good at understanding how other people think and getting in their mind set - even if retarded at figuring how they are feeling - so they can get a really good idea of exactly why people have problems and never being the type to shy away from the truth will tell you the answer when other "tactfully" won't.
I think the ENTP isn't as good at it because there not as good at focusing on the problem and really analysing it as deeply. Also ENTPs have a tendancy to see "the problem" as not a problem, just the person caring too much.
If they put their mind to it though there as good at it as INTPs - and also have a slightly easier time understanding emotions.