Let me repeat again. PII is a crutch used for matching, because current matching/segmenting technologies are crude.

Advertisers don't want PII. What they want is target audiences with predictive power, which means data sets where the central limit theorem holds sway. (I.e., thousands and millions of people lumped together.)

If advertisers could get at these segments directly without PII, they'd do it in a second.

Like I said, knowing real identities is the last thing on the list of ad tech priorities.

If shadowy entities are collecting "real identities" then it's not for ad purposes.

Only if they're clueless.

For example: Nike really wants a dataset of "people who buy expensive sneakers for fashion purposes".

This dataset is probably hundreds of millions of anonymous people, and not personal data. If there was a way to get this dataset directly, Nike would do that in a heartbeat.

Unfortunately, as of 2019 the only way to get something like this today is by, e.g., crossreferencing credit card purchase info with Twitter browsing logs, which leaks a shitload of sensitive private data.

For ad purposes personal data collection is a bug, not a feature.

Advertising is applied sociology. As such, advertisers want to aggregate large data sets into large segments that are easy to manipulate statistically. (Where the central limit theorem starts working.)

There is no demand for personal data or de-anonymization because that stuff doesn't sell.

The personal data collection is done by Google, Facebook at al not for advertising purposes. They're collecting it because they view it as a resource and a currency in the future de-anonymized world. (Think China's "social capital" except on a larger scale.)

Source: I've worked in the ad industry for over 15 years.

This in contrast to "sysadmin who can configure your Cisco and your Outlook".

The difference is crucial in data centers where you need automation for sysadmin tasks. (I.e., all of them.)