One other thing they give you at a large organization is flexibility in your stack

If a team wants to try out a different language, or hosting model, or even just framework/tooling, those things can be really hard to do within the same codebase; much easier when your only contract is handling JSON requests. And if your whole organization is totally locked into a single stack, it's hard to keep evolving on some axes

(I'm generally against microservices, but this is one of the more compelling arguments I've heard for them, though it still wouldn't mean you need to eagerly break things up without a specific reason)