These all have the property which is that they are scarce physical goods or services. Software is not scarce (though of course the labor to create it is), so this is a really bad comparison.
And again I did not say it should or should not be free, I said there are engineering benefits to open source software and more and more people recognize those benefits and choose to make things free because they see the value and are willing to recognize the tradeoffs. I never said what "should" be done. "Should" is kind of a nonsense term when used in this way as it hides a lot of assumptions, so I generally do not use it, and notably did not use it in my comment. I want to point out the peculiarity in your rather strong response to a word and concept I never used. I think you are having an argument with imagined people, not a discussion with me.
And for what it is worth, I am a robotics engineer and I am designing a completely open source solar powered farming robot designed to be made in a small shop in any city in the world (see my profile), funded by a wealthy robotics entrepreneur who recognizes the value in making this technology available to people all over the world.
So I am one of those engineers making this choice, and not someone just asking for things without doing the same of my work. Everything I produce is open source, including person projects and even my personal writing.