Writings on the rear window of cars

Why do people have writings on their car's rear window? This is a question that hovers in my mind every time I see one.

Some of them have religious sayings or quotes that glorify gods of the respective faiths written on the rear windows. This probably stems from a belief that god would watch over them and make sure they are safe always. It could also be a way of showing off their religious inclination. 

Others have names of their family members (usually names of children) written on the rear window. When I come across these kind of writings, it makes me wonder why these people would want to share the names of their family members for the whole world to see. What do they gain out of this? Is this a gesture of the love and affection they have for them? If yes, why do they want to announce it to the world?

I am often compelled to ask the drivers of these cars or vehicles on why they do this. I guess many of them just mimic what others do.

Apart from these two types, I have also seen some funny, weird or quirky messages written on the rear windows. That is done when vehicle is usually owned by the younger generation.

It is each one's right to do what they want to do to their car.

Personally, I like to keep my car windows plain and clear without any writings or drawings on them.