My Model S is my daily driver
My Model S is my daily driver and I own no other car. Additionally, I know many Tesla Model S owners in Houston (there are over 400 cars in Houston now) and I know of no owner which uses the Model S as a secondary car. So in Houston at least, your premise that the Model S is just a secondary vehicle seems to be false. If you are looking at families and car ownership, if you look outside of major cities like New York and Chicago, I'm sure you will find that families own at least two cars, but generally because both adults in the family each have a daily driver.