No one wakes up excited to see more advertising, no one goes to sleep thinking about the ads they’ll see tomorrow. We know people go to sleep excited about who they chatted with that day (and disappointed about who they didn’t). We want WhatsApp to be the product that keeps you awake… and that you reach for in the morning. No one jumps up from a nap and runs to see an advertisement.
“Why We Don’t Sell Ads”