Trails are on my Fenix 6xPro but not my 66 - Why?

On my Fenix, I have virtually every trail on my map which is fantastic.  However, on my 66, with topo 24K maps purchased, I have no trails (unless I download the specific gpx file).  They aren't in the maps.  So why can i get trails on my tiny watch screen but not my fantastic 66 screen?