Because WhatsApp uses your phone book as the only way to interact with its contact list. You can't add someone to directly to your WhatsApp contact list.
It could probably access it less often by only sending deltas, but that would mean their servers would have to store your whole phone book. I don't think that's any better from a privacy perspective.
Of course Facebook Messenger doesn't do the same, it has its own contact list coming from Facebook.
It could probably access it less often by only sending deltas, but that would mean their servers would have to store your whole phone book. I don't think that's any better from a privacy perspective.
Of course Facebook Messenger doesn't do the same, it has its own contact list coming from Facebook.