Creating a “pile as many people into a slack channel as possible and thus dilute the accountability” model that happens. Accounts demand accountability: people are specifically on the hook for the overall management and health of the account. They need to ask for help and engage and disengage with other teams as needed. When 10 or 50 people are weighing in, it's never good for the client.
Mass-production has a harder time scaling in Saas, because some saas isn't meant to scale. And once you start the habit of throwing people at a problem, you unknowingly start becoming a services company.