What actually changes between static and rotating?
Ownership and duration. A static residential ISP proxy is an address assigned to you: you know its identity, you know how hard you have pushed it, and it is still there tomorrow. A rotating proxy is a request for an address from a pool you share with other customers — you get residential reputation without knowing, or controlling, which specific IP carried any given request.
Everything else follows from that. Debuggability, per-IP health tracking, and session continuity come from ownership. Sheer address diversity comes from the shared pool.