Many years ago, we made the decision that clients we provide server hosting to as part of service would use their own server lease account, rather than using an account that could share several domains in the same server lease.
When you design and maintain WordPress sites, there’s always the opportunity for the client to completely take over the entirety of the web site, from hosting to maintenance to site development to security. To be honest, we rarely see this happen anymore, but it is the client’s website, they decide the long-term direction of it, and we want to be accommodating and flexible within that understanding.
By using a unique server lease account for each client, this allows for the transfer of a client’s site WITH server space fairly easy. We can simply transfer the account to their control (and direct payment).
This also allows us to allocate specific server resources per client rather than forcing them all to share the same resources. It theoretically provides some greater security since there are less admins per server account. And because we can’t guarantee the actions of a client acting as admin, we don’t want other clients incurring any risk from a client’s behavior.
We know some web developers have their clients share their server lease account. There are reasons for that, particularly in ease of setup and in server fees. But those reasons matter less to us than the reasons we value in not doing that.