A common refrain from parents in these situations is how strong they thought their relationship with their child was and how they never imagined it could happen to them. Thats scary. Weighing a very low probability extreme consequence vs. various questionably impactful interventions with certain downsides is hard (at least in my view).
Not to mention that there are risks the internet exposes you to that aren't sexual abuse related. Desensitization to violence, insane discourse (epithets dropped like candy), etc are also important aspects of a parent's moderation choices. Trust and conversations cannot address this since the desensitization takes place as a consequence of simple repeated exposure. In the extreme case, desensitization translates to usage, and I think thats clear if you listen to any 14 year old kid on an xbox stream.