I don’t think the existence of a roadmap innately helps the development of a live service game. Anthem launched with a roadmap and that game crashed and burned, got back up, flipped, then exploded.
I think there is probably a solid internal benefit of not committing to anything before you know if you can handle it or not. It seems like during the development of Infinite there was a lot of changing up with the management of the studio. Something like that can really throw off development and cloud up their view of the future. If I were in the dev’s shoes, I would also want to keep a tight lid on what future expectations should be. Not out of some entitled sense of dishonesty, but out of a pragmatic sense of caution.