It happens when you change your plans to the next level. Here, the next level in the sense, transferring your plan from an existing shared hosting account to a reseller account or to a dedicated server plan. Like the same, it happens when a reseller account has to be changed to a vps or cloud or a dedicated server.
And the server is never changed if you are just going to upgrade your basic hosting package Fundamenta Romeo to a slightly bigger Husky Romeo and same happens if you are upgrading your web hosting account from Husky Romeo package to Jumbo Romeo.