I never understood why they never brought him back, it made a ton of sense for Peach to have a dedicated butler and for him to be in charge of the other Toads. But he was just a one-off character forever doomed because Nintendo hates the GameCube.
TIL, he's still well appreciated in the spin-offs. But a lot of those are pretty old games by now, it'd be nice to see him as well as any other favourites in a mainline Mario game.