I think tastes change for people who collect. Yours is a very natural progression. You have plenty of the more common machines so now you are beginning to seek out other less common machines. I think price becomes less of a factor too. Things like rarity and condition become more important to those who have collected anything for a while.
While I love the fun styling and colors of the dashboard machines it seems I have more of an affinity for old black machines. For whatever reason those ones speak to me more.
Rodney