[rjpr]

Probably because Google is treating all s3.amazonaws.com links as being the same authoritative site, so they see each of these coupon sites as just a page of s3.amazonaws.com and therefore the site gets the link 'juice' from the root s3.aws domain.

Each page of a site doesn't need a ton of links to that specific page to rank, just links to the site in general (site being root link plus subdomains).

That's typically why blogspot-type services give you a subdomain, and not a page on their main domain.

It's been known about in SEO circles for a while[0], will be interesting to see if things change in the next major Google update.

[0] https://www.blackhatworld.com/seo/how-to-get-backlinks-from-...