I think that is a little unfair. I don't know anything about the companies behind Redis and Elastic. But another possibility is that they want to make a good open source product and create some sort of business around it and find it difficult to make a waterproof moat. I'm sure that there are many other open source companies with the same basic strategy that are just more lucky, e.g. don't get AWS as competition.
This isn't complicated. It's trade secrets 101.
I'm being disingenuous though. Of course the bait-and-switch merchants know this, they're just banking on getting enough product momentum off the free labour of others before they cash in. That's the plan all along.