You can easily damage a persons reputation, make them unemployable or social outcasts, create an environment damaging to their mental health without any proof. Believing that the public will dismiss claims, just because you stay that there's no proof is rather naive.

A Danish newspaper at one point falsely claimed that a named person had raped a child, with no evidence. The only way that person escaped public judgement was by going into full attack mode and publicly suing and attacking the newspaper and the reporter. You have to be an incredibly strong and resourceful person to do that and not just go into hiding. Also one thing is suing a Danish newspaper, imagine the legal team, the resources, you face if you're trying to take Google to court for defamation.