The value is consolidation. Without a gateway, every service needs its own authentication check, its own rate limiter and its own logging format, and they inevitably drift apart. Centralising those concerns means one place to change a policy and one consistent implementation to audit.
The corresponding risk is that a gateway is a single point of failure and, if allowed, a place where business logic accumulates. A gateway that starts transforming payloads and making routing decisions based on domain rules becomes a distributed monolith's worst component — shared by everyone, owned by no one. Keep it to cross-cutting concerns.
Codazz builds this in production — API & Backend Development.