That's never strictly true. Companies will always pay FOSS companies for hosting so that they won't have to manage or be responsible for their own self-hosted version. Most self-hosted versions are used by small companies/devs or companies who need constant audits (i.e. Healthcare). They were making everything available for free, plus free image hosting, and gave no real advantage to paid users beyond choosing your Docker version (no forced upgrades) and extra hosting space.

As an adjacent example, AWS makes big dollars on all their services - which are almost all FOSS projects they themselves had no part in making - just by hosting and configuring for the customers.

Docker was just a bad FOSS model for profit, and they're trying to overcorrect to become sustainable.