Or it could be because of the weird old timey sentence structure. And it’s actually equivalent to:

Why do you call me (the Lord), “Lord”

Similar to “Why do you call me, your boss, ‘Boss’, but then don’t do the things I tell you to.”

Once to establish “I am Lord” and once to establish “And you call me that”.

Either way, it’s a translation, and not the original text anyway. So I dont know why people feel the need to put borderline gibberish on the side of their car.