"those people are pure engineers, that don't know/are not interested in business, marketing, making a product out of their software, etc.. practically anything besides coding"Yeah, that's a serious problem, and one similar to ones that artists and musicians face.
I've made a fair bit of art (paintings, drawings, sculptures) but except for one group exhibit in high school I've never bothered to exhibit it anywhere, sell it online, or show it to anyone apart from family members and a few friends (and even they haven't seen most of my art). It's just too much trouble. I'd like to make a living making art, and have considered creating an Etsy page or something, but have never gotten around to it. So I just keep making art for myself.
I also make music, and have kept that mostly to myself for the same reason. I've uploaded a fraction of it to Soundcloud, but I don't advertise it in any way, so even finding it on Soundcloud would be almost impossible for someone if they didn't search for specific keywords that I've tagged my music with. Mostly I don't bother even uploading it, though. It's too much trouble to record, edit, name, upload, provide metadata to Soundcloud and find an image to go with the track. So I just tend to keep the music to myself.
I've also written quite a bit of software over the years, and have open sourced some of it, and am a big believer in open source, but it's just too much trouble for me to package stuff nicely, write readmes for my software, and make sure the software is decoupled enough from my own environment to be useful/buildable for someone else, so a lot of it has just kind of rotted away on my hard drive for decades without anyone else even knowing of its existence. So I mostly just write this code for myself.
Some people go all out to promote their software, music, or art, but that's just not me. For me the joy is in the creation, and the rest is just not important enough.
Kudos to all those people who actually go to the trouble of open sourcing their code, release music to the public, or show their art. I know how much work just doing that can be, never mind trying to make a living at it.
That said, if you are willing to go to the trouble, there are successful open source projects which manage to make money that you could model your own projects on.