Yep differentiation is tricky here. Chainguard are expanding out to VM images and programming language repos, but the core of hardened container images has a lot of options.
The question I'd be interested in is, outside of markets where there's a lot of compliance requirements, how much demand is there for this as a paid service...
People like lower CVE images, but are they willing to pay for them. I guess that's an advantage for Docker's offering. If it's free there is less friction to trying it out compared to a commercial offering.
Depends what type of shop. If you're in a big dinosaur org and you 'roll your own' that ends up having a vulnerability, you get fired. If you pay someone else and it ends up having a vulnerability you get to blame it on the vendor.