> nor the complete mapping of customers behaviors to use in contexts not being the phone call

This is because the telephone system was regulated with wiretapping laws, among others.

> I don’t remember reading about ads in phone calls

See above, but also: Junk Faxes & Telemarketing/Robocalls.

> The apples to oranges in this comparison is probably top five on HN ever.

It all comes down to whether you view social media as a communications platform or a publishing platform.

The strict regulations governing the telephone system (see above) would adequately cover both with deliciously-antique turns of phrase like "wiretap" and "pen register".