One of the worst design decisions of Unix to fundamentally separate the source from the binaries. And Debian and those of their ilk had to make it worse with that -dev package nonsense.
I only know that windows does something different more akin to debug symbols in each binary by default with chicanery to not have it impact things in the general case. But I'm not a windows programmer this is about as much as I know about windows in that regard.
And that leaves no current viable alternatives to the Unix-like systems. Sad, really.
What made Unix a success is a great mystery to me. Presumably it was the ability to run a time-sharing system on low-cost hardware, but then people started taking the tradeoffs it had to make as gospel, which is why we have this ridiculous situation of still wrangling processes on computers with 64 bit bloody address spaces.)
btw: so are you advocating a full GPL-like distribution of the sources alongsides the binaries for all programs?
Not the parent, but I definitely advocate for that, so long as it maintains user freedom.