I didn’t see it mentioned but a common use case for 3rd party cookies is correlating session data across your own multiple domains (if your company owns multiple domains). Publishing companies typically own multiple domains/verticals and can increase ad revenue / seo / traffic quality by linking properties together. It’s important to be niche as a site (verticalization) but also broad as a publishing operation (own many verticals and shift your marketing spend daily).

Anyways, google has been writing a spec for “first party sets” to help replace the use of a 3rd party cookie to connect domains you own. https://github.com/privacycg/first-party-sets

I believe this will need to be implemented before Chrome moves aggressively against 3rd party cookies.