Generally speaking, business to business customers expect a certain amount of investment from your company into integrating with them when they offer you a contract.
"Sells itself" means the product able to stand on its own and raise awareness without paying for advertising to do it.
You of course need people to sign contracts & complete the purchase, that's irrelevant to how well the product is able to raise awareness without advertising, i.e. people interested in buying Tesla's didn't hear about it through any of their advertising.
They have an enormous B2B sales team.
Sales reps are for B2B, not B2C.
Generally speaking, business to business customers expect a certain amount of investment from your company into integrating with them when they offer you a contract.
Sales is part of this.