Mostly just the intuitiveness of the architecture. I don't need bi-directional if I'm mostly just showing you some forms in a CRUD app, and client-initiated request/response is simpler to reason about.
Bi-directional gives you more power, but you also have to think harder about the protocol and application state once the server is also pushing events to the client unprompted.
Bi-directional gives you more power, but you also have to think harder about the protocol and application state once the server is also pushing events to the client unprompted.