Yes, I also buy CoD for SP. I stopped caring about online after MW2.
But I also know what I'm going to get with campaign and I know it will be short. Anybody who complains about the shortness of CoD should know better.
But in the end, at least there is usually 3 portions to a CoD game even with some people only play one part of the game.
But The Order is a single player game only and having a SP campaign about 5-6 hours is pretty weak.