They did.
Link : https://tcrf.net/Sonic_Adventure_(Dreamcast)
Well, if we ever get a remaster, they could probably add them back in.
Yes, this is really changing the lore we knew, but at least it's for the sake of gameplay.
Isn't gameplay what matter most in a game?
Plus, I have a feeling that Sonic Frontiers will be tied in with Sonic Superstars some way or another. I mean the Special Stages, or at least possibly the Bonus Stages, they look like they take place in some sort of digital dimension. So if Northstar Island is in the vicinity of Starfal Islands or have Ancient tech on it, I wouldn't be surprised if the Chaos Emeralds individual powers were due to
cyber space.