Because the cost of a contract initiation on a DAO is much less than that expensive lawyer you must hire to make that LLC a reality. Your LLC collects the funds but in exchange, you can't issue a security that easily. Selling shares to random online folk isn't easy either. But the most important thing is convincing people. DAOs are now an initiated concept. A centralized version of that needs to emerge again and find its stable model over many years, just like DAOs. This will hopefully happen.