It probably has a lot to do with the age gap and new fans post 2008. If there were fans that started following them this year they would probably look at PP and think he was washed up (without enjoying or really knowing what he brought to the team).
Also, the previous years during the playoffs, when I would be on game threads on different websites it was always about what Rondo was going to do that night. Everyone knew PP was the Truth and could hit big shots, but people wanted to see Rondo because he has flare.