It’s not so much a question of allowing it, it is just not being done by LineageOS themselves. I suspect reasons like resources and focus.
You are perfectly allowed to build your own LineageOS.
Almost no halfway current piece of software ever is 100% finished.
That’s why I asked for a specific problem, because quite a lot of users here use 16.0 as their daily driver, including me (LineageOS for microG, though, which is based on official LineageOS).
Cautious concerning a version jump, yes, but rather less cautious concerning security holes 
.
That’s legitimate of course, we all have our own priorities.
If it helps, I tend to check whether the basics work when I install a new build. You can have a look here.
If you miss a basic check you would like to see, feel free to tell, I’ll see what I can do.