If you're asking why somebody would use it instead of something already here, take a look at
these examples. Why would you not consider using an Ethereum contract before starting a large Java project, for example?
Anyway, I agree with CoinHoarder; I don't think any answer will satisfy you.
It would help us all if you could read.
I said take an existing platform and add your feature to it -- not take nothing and add decentralization and your feature to it.