Looking ahead for WhatsApp
Funny how times change...Some quotes from a What's App blog post from 4 years ago titled "Why we don't sell ads"[0]  "Remember, when advertising is involved you the user are the product."

  "Your data isn't even in the picture. We are simply not interested in any of it."

  "When people ask us why we charge for WhatsApp, we say "Have you considered the alternative?"

So they aren't showing ads themselves, but they are shipping your data out to another entity that is. Seems worse to me.[0] - https://blog.whatsapp.com/245/Why-we-dont-sell-ads?