Groove has such a range of customers they want everyone to know their product can work for their small business.
Your customers know their previous pain-points. Here's a Customer.io success story.
Vimeo is a Smartling customer who has market name recognition. "It just works" was a great line to have from an existing customer.
Often a product will have multiple people making the buying decision. Accountants are often the gatekeeper to the SMB market.
Your customers can oftentimes relate better to your potential customers better than you can.