Huh? I didn’t give away my contact list. Neither to Facebook nor to Signal. As I said you can use Signal without allowing access to contacts. You can enter telephone numbers directly. Was I being unclear?

You gave your contacts either to Apple, or to Google, by using their OSes.

I would expect Apple not to sell this data. They don’t need to, and the bad press if it gets exposed could loose them more money. Their business model doesn’t require it.

Facebook is not selling this data too, afaik. It's too valuable. They are using it to target paid ads. Apple's ads business is still in its infancy, but it will inevitably grow bigger to justify their share price. I beleive, however, that at least their music recommendation system is lavishly fed on their social graph data.