WhatsApp is over 4 years old with over 300 million (claimed) active users. I would expect them to have addressed security by this point. Especially after their previous blunders, I'd imagine hiring a security expert or having a third party audit their code being on the top of their list. Apparently not.

I think these news and concerns often don't make their way to a bulk of their users, who probably aren't very tech savvy. If they don't see any user defection as a result of these issues being uncovered, then I'm not surprised about their lax stance on security.