Mainly because I know for lots of personal experience that within an hour of me discussing any of my feelings to them, they'll have completely wiped it from their minds and proceed to do or say things that are thoughtless and insensitive just for the sake of interacting with other people.
I have yet to meet a single ENTP capable of handling or understanding feelings to any great degree. They know how to make people happy, get others involved and excited, (and I envy many ENTPs for it), but it's a very personally guided process.
When it comes to more intimate situations driven by individual people's feelings, ENTPs don't just falter... they trip over the pavement and break their heads off the grounds.
ENTPs are about bettering themselves, INFJs are about bettering others. ENTPs are good at getting people outside of their shells, INFJs are good at helping people get inside themselves.
It's a complicated dichotomy. I understand why it works for a lot of people, but I'm a very emotionally sensitive individual and it's never worked for me. I can't stand emotional insensitivity, and ENTPs fall back on it a little too often for my tastes. That said, unlike many INTPs, they at least know how to feel guilty about it.