Because opposition parties generally have their groups in there, which would cause political backlash and distance the supporters that still use it. Not that banning social networks abusing their privilege through hidden moderation and promotion and selling their user's data so propagandist know who and how to target shouldn't be done, but right know it would be done under the counter-chants of "repression" in the particular cold war 2.0 state of affairs of the world today, and that's very politically taxing.