On iOS, the average user has a chance to download that mainstream app and deny it access to their contacts.
That sounds like you meant it as a rhetorical question, but "yes" is a reasonable answer.
> are [most people] really going to forgo having Facebook [...]
There will certainly always be people who do pay attention to permissions for privacy or security reasons, but they seem* vastly outnumbered by the people who don't.
* Just an intuitive sense, I have not looked for data to back this up.
Also, the development cost of 'does this feature exist?' for each permission is pretty high.
Then Facebook Lite came out, and it was what I wanted all along.