Imagine if, when a Windows version became outdated (So anything before Windows 8, I guess), Microsoft made it available in the public domain.

We could have Windows distributions, just like Linux! Imagine how weird it would sound if you just said to your Linux-using friend, 'Oh yeah, I use arch!' and they replied 'Oh, me too! I love Arch Linux!', and you just stare at them and say:

'What's Linux? I only use Arch Windows.'

...
...
...

'Arch Windows? Are you stupid?', they would reply in utter disbelief.

We all know someone's gonna blurt out 'Yeah guys! I just downloaded Kali Windows so I could learn to hack, I don't know what you're talking about!'

Ah, good times.