Because the previous ways of communicating while working for a company with a compliance department that are hard to subpoena weren't on hundreds of millions of

Because the previous ways of communicating while working for a company with a compliance department that are hard to subpoena weren't on hundreds of millions of people's cell phones? Not saying that means the law should go after WhatsApp or it's WhatsApp's fault (I would strongly argue against both), but that doesn't mean it being made easier and deniability becoming more plausible isn't the cause.