Jon and Richie are the main songwriters the main showmans and they are the ones who promote the albums, because they are the ones the media wants to see.

Tico and Dave while I respect them and value their contributions to the band they don't write (outside of secret Dreams Tico doesn't have any other songwriting credit and Dave only has a couple) and the media doesn't seem to be near as interested in them as they do with Jon and Richie.

And aparently on this tour at least, Dave isn't the one and only man on the keys anymore.