If paying for docker affects your bottom line, you have bigger problems. In the meantime, not paying things creates a tragedy of the commons and distorts the market (by giving an advantage to incumbents who earn money on other things).
Some companies are probably not far away from technical collapse if a few of their critical open source libraries and tooling go to shit. Better cough up a little bit now than have to fork in the future and set up a whole new team to maintain that dependency - likely with much worse results than before.
