The full color manga draws a distinction between the Saiyan and Freeza sagas, I think the main reason it's not as popular as the other three post-23rd is because Vegeta became an anti-hero and then a genuine ally of Galu, plus it was revealed that Freeza was behind the Saiyans' destruction and most of the plot points from the Saiyan arc like Scouters and space travel carry directly into the Freeza saga.
even in dragonball-kai, the poster, sets & stuff call just the freeza-saga, even-tho the poster also had vegeta so he is significant enough to be still highlighted exclusively
Because of Vegeta's popularity I think. He was over enough to have a saga on his own and separate from Freeza. Pretty impressive for Toriyama managed to create popular villains back to back.