I understand their Enterprise offering offsets the costs of hosting the open source version for you. But should another product be the dependency of determining if the open source version is free? What if the Enterprise offering stops making money? Wouldn't you rather pay for the service you use so it supports future development? It's like Apple depending on product A to give away B for free, that doesn't seem like it'd scale a whole lot. Product B will just reach into the resources needed to build and manage product A.
Just my 2c anyways, happy to hear feedback on why I'm wrong :)
Because businesses need money to survive and most have no problem spending it when it increases productivity or provides perceived value over another product.
If every organization went to free alternatives, not only would those free alternatives need a source of revenue to support the new business, I think you'd find they too will change their pricing structure to better fit the people that use their product.
One thing I also have to mention is a majority of for profit organizations have no problem paying for services they use. HN is a special snowflake on the internet, it's not a reliable source of market research by any means.
I can guarantee you none of the competitors are in it to provide a charity. They all want and NEED to make money somehow, I think you'll be surprised how long free solutions tend to last.