@Michel B I don't think for an end user software developer like me, it is quite prudent not to have the same version of the system as what currently sold machines have. The alternative being to have a pull of beta testers using High Sierra...
Ironically I actually agree with your statement, but don't do it. I am not a fast developer, it can take me a long time to develop an application and after the dog shite that was Yosemite, I became concerned about how much time I spend doing Apple's Q/A for them rather than working on my apps. So I stopped beta testing the macOS at El Cap. I test my apps periodically and report bugs, but that's about it.
I do have a second machine that I use for almost everything else than programming and that has two partitions, 1 Yosemite and 1 whatEverCrap we have this year. I try to use it with the latest OS, but when it gets too frustrating I go back to Yosemite.
@Helge T I upgrade as soon as it comes out... :)
I used to be like that, right since the days of System 7, many times I've been able to do serious work with beta OS versions. Just the last 3 OS releases have been utter tripe during the beta stage. I know that this isn't reflective of everyone, I know I almost always seem to be going against the grain.