The Rohirrim, why horses?

[Rhugga II]

Originally Posted by Rumil

As said, the Rohirrim had no reason to lose their horse-addiction, in fact they moved from an area in the Upper Anduin that was likely OK horse country down to Rohan that was excellent horse country - so no reason to change.

Maybe this comes from MERP, but I can't get it out of my head that when the Eotheod lived East of Mirkwood, they were called the Eothraim? Anyway, the rolling plains that stretch from Erebor to Rhun would certainly be conducive to a nomadic horse-culture. This being said, the Upper Vales are significantly different. The area near Framsburg was colder than the eastern plains and was comprised of hills and undulating lowlands. Rohirric culture, with its holds (Edoras, Helm's Deep, and Dunharrow), seems to be an amalgamation of the old nomadic culture of the East and the more sedentary hill-dwelling culture of the Upper Vales.