While I have ublock on my laptop, i still get ads when I am on my phone which ironically is where these companies get most of their revenue these days.
[1]: https://pi-hole.net/
[2]: https://adguard.com/en/adguard-ios-pro/overview.html
Even if you install a root cert to MITM, some apps pin certs.
If you have persistence, no jailbreak is needed. Would require you to binary patch the executable then resign the binary using your own Apple Dev account. Far from trivial, but still doable and without Jailbreaking.
Generally, you should be using Firefox, not Chrome, with Ublock and/or Umatrix installed to maintain control of your web experience. FB web interface can be used and ads generally blocked. Reddit's native ads are served directly via first party URLs so it is tuff to block. Reddit's made changes for the advertisers and their new UI is meant to popularize Native ads.
He is the CEO of a technology company.
The necessary knowledge about the existence of content blockers as well as the technological literacy to set them up is probably a given.
He also probably has a high value attached to his attention, given that he is in quite a power position. This, I'd argue, would make a greater reflection of media habits more likely.
Additionally there might be the security/privacy aspect. Executives should really focus on security as their devices might be of greater value than your average grandmother's Scrabble tablet.
However I think that it is not very speculative to say that, if more people knew about content blocking, more people would block unwanted content. My intention behind assuming his knowledge/competence was only meant to exclude nescience from the list of potential reasons for him to not block content.
Personally I'm thinking that since he's the CEO of a company which monetizes on ads it could be that he wants to follow ad trends, see what's going on in the ad space, what other people are advertising etc.