We all know that if we want to use ArcGIS Desktop 10.x styles with ArcGIS Pro, we must import them into our Pro project as an imported style.
Pro also has a limited number of native styles in contrast to what Desktop has available.
It's one more step for map creation in ArcGIS Pro, when you want to use a symbology from a style that was available in ArcMap (ArcGIS Desktop 10.x)
Many users, such as myself, rely on those Desktop styles to author maps and it's perplexing why so many styles were made available in one platform, but not another.
Further, if the effort is to win the hearts and minds of seasoned Desktop users to convert to Pro, it would seem logical to make sure the styles and symbologies that are available in ArcMap are natively accessible in ArcGIS Pro.
One day, we won't need to install ArcGIS Desktop because Pro has all the functionality we need, hopefully? Migrating the existing styles from ArcGIS Desktop to ArcGIS Pro would help that transition!