Excitebike series mostly stress on vehicles, not characters. They only have some Excitebots and riders with names in Excitebike 64.
Some old game characters don't have the clear retro appearances like Nana&Popo do. And probably newer games with sequels have the priority because some classics don't.
My roster has Retro characters, and I still fit in Waluigi (I don't think Daisy would be a good Brawler).