How do free apps earn money without ads?

Question

Take example of whatsapp, google maps or this sololearn app

Answer 1

Most of the times, there are ads, but just not intrusive enough to annoy you.
https://www.quora.com/How-does-WhatsApp-make-money-36
(For Google: HA! Have you seen them dem ads on YT brah?! These guys rollin'in money smokin' diamond cookies like nothin')
As for SL, we go by public funding.
https://www.google.com/amp/s/techcrunch.com/2016/10/18/sololearn-raises-a-1-2m-seed-round-to-socialize-mobile-code-learning-via-its-app/amp/

Answer 2

If your app has enough
popularity you can sell
customers data (bad but practiced)
or you sell the app ownership
#ideas

Answer 3

they have investors or they collect data about users and sell it