Why is it...

When Mopar guys are talking about camshafts, they seem to refer to lift. For example, "I have a .590 cam in my....".

In my past experience with Brand X, camshafts are referred to by their duration, either advertised or at .050. It seems duration is more relevant when discussing cams because it tells you how streetable the cam is, and if it'll require stall/headers/gear.

So were the old Purple cams advertised by their lift? I'm just curious as to where this started.