I’ve been meaning to answer this for ages; I’m sorry.
I think they get the least attention because they don’t have many direct connections to Harry’s story; the name of the every book is Harry Potter and the _______. Actually I think Rowling has said something along those lines before.
As for why I think they don’t have many connections in the story: Gryffindor is the brave, therefore always doing something heroic, making for a good story. Slytherin the cunning, often leading to conflict, also making for a good story. Although they also don’t get to big of a part in the books, Ravenclaw is the wit, great for helping the story along.
Hufflepuff generally stay out of the attention by nature anyways, so it makes sense that they wouldn’t necessarily do leading the fight against or for Voldemort, which is the main plot of the books.