The Turing-completeness of the language is the whole point of Ethereum. That's what differentiates it from other (Bitcoin-like) crypto currencies. It allows anyone to build arbitrary business logic--an exchange, a venture capital firm, a game--that is run directly by the participants in the blockchain.

In retrospect, a declarative language might have been a better choice. There's a tendency in open-source projects to make things Turing-complete because it's too hard to agree on what the declarative primitives ought to be. (Hence JavaScript.) This is not what you want in contracts for substantial amounts of money. It's passing the buck to the users.