We make our judgement on the trustworthiness of a vendor very quickly. With standard emails it can be exceptionally hard to get your personality across.
With a short personal video you have facial expression and tone that can help humanize your company and build a genuine connection.
For production grade video every small factor from lighting to make-up is accounted for. For personal video it is all about being relatable, so there is no need to be hyper polished. In fact, having your co-worker wave to you in the halls or tripping while you are attempting to record your video makes you that much more “human” to the customer.