Registering in Germany

There is a procedure in Germany where you must register with the town that you live in. They must have your name, address, marital status and religion for their records. When you move town, you unregister there and tell the next town.

Now as much as I keep asking "why" this is necessary and I keep getting the answer (mainly from locals and government workers) as "Because it is law", to me, this still isn't enough of a reason. Especially, why do they need to know what religion I am. I'm told that is for taxing purposes (you pay a tax to your church here), but I still find it a little intrusive for the government to be tracking my religion. I also was told, that its a good way to find me if the government needs me from this information, its how the German government can track me down 'if they need me'…. 

The only other reason I could find was stated on a random website that:

"Registering is also necessary for getting power, water, phones etc hooked up and correctly billed. While these folks do not demand to see proof of registration, they do all tie their records together once you are signed up. As an example, if you buy a pre-paid mobile phone ticket, you must give an address and, if that it not registered, the pre-paid phone will not work!"

But that still doesn't quite answer why..? Then the government needs to know your water, power and phone usage also depending on where you live?

I'm sure there are people out there who actually have the facts, and good ones as to why the government needs this exact information for every movement in your life - that are less conspiracy theory sounding that what I have stated above - and feel free to post that reason below, but it would be nice if everyone knew this reason rather than just telling me "because it is so". 

Side note: This "because it is so" is a common answer to many of my questions.