Ps. I am proud that I was a paid co-developer of the very first distribution listed ;).
You don't think the lessons learned by those developers' experimentation weren't shared and applied in the decision-making process for more prominent distros? In a way, creating a distro is like contributing to all the other distros at the same time. What makes them fine developers is their drive to innovate and try new things so that one day the status quo can improve. Who knows: if all those developers worked on the same few distributions, they may have crashed and burned.
Sometimes. But there is also a lot of 'let's take Ubuntu and change the default desktop/wallpaper/DVD package set/...'.
Also, it's not as if developers in major distributions such as Debian don't have room to experiment with different approaches. For instance, in Debian, the default init system discussion rages. The most promising candidates are already available in Debian itself.
I know it's cool to be all blase about this, but this is different.
Many of us bear scars from trying to write portable software across commercial UNIX systems, while discovering that POSIX only covered part of the required features, and even the POSIX ones had implementation defined behaviours.
Not to mention the wonders of each system having their own UI toolkits, besides each XWindows flavour.
I did it between AIX, HP-UX, Solaris, Xenix, DG/UX.