Are you or anyone you know so dedicated or loyal to one railroad, either real or fantasy, that you run only that road name and no other railroad(s) on your layout? Is your loyalty so strong you wouldn't purchase any locomotive or rolling stock, if it didn't have your favorite railroad's name irregardless of how much you liked the appearance or features of another railroad's item and yearned for that particular engine or type of rolling stock in your favorite railroad's name?
I should add my question of such extreme loyalty also extends to shelf queens you might have and in fact to your ENTIRE collection.
Btw, I'm not referring to manufacturer loyalty such as buying only Lionel, MTH, Atlas, Williams, etc. but strictly loyalty to a particular roadname.