Well, yes, we are creative goofballs, but I personally can come across as very T, as I am a lawschool grad who was raised by an ISTJ lawyer on a mission to convert me to T. My first instinct on Obama was INTJ -- cool, rational, analytical. Still, he has some real NF qualities in his speechifyin' and even if he isn't writing them, the delivery... WOW. So, I could see ENFJ as well. Not sure. Whatever he is, he's very well rounded, I'd say, with strong iNtuition, Feeling and Thinking.
It seems to me that Lincoln was very introverted, from what I've read of him, but maybe NF. INFJ, rather than ENFJ maybe?
Reagan, no idea, no T there though I don't think and no introversion.
Carter could be an NF. He seems pretty idealistic to me.
I wonder if some sites claim there are no NFs simply because an NF would have to develop by balancing those traits in order to make it to the presidency, so their NF is somewhat hidden to those who don't know them well.