Most venues will not require proof of general liability insurance. However, some of your larger venues will require vendors to have proof. Prior to hiring any vendors you should check with your venue if they require any proof of insurance. Often time's vendors require a deposit or payment prior to the event. If you find out that they don't have the proper insurance you may be out of your deposit or loose part of your payment.
Why wouldn't you want to make sure your vendor has insurance? Don't you want comfort knowing that should any accident occur that you and your guest are covered?