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People rarely make telescope mirrors of this size at home, it just takes way, way too long. As mirror radius increases the amount of material you have to (very slowly) grows in a cubic fashion, so a 14.7" mirror requires removing over 8 times as much as a 7" mirror. It takes too long to do this by hand to be reasonable for most people.

Given that all commercial mirrors are made by machines and computers, why not the same at home?

The jig to do it is somewhat expensive it and hard to put together. The especially hard part is getting the lens to not vibrate at higher speeds, which is probably done by using pneumatic or hydraulic drive or very strong magnetic drive.

And if the thing goes off, you could have tens of kilos of broken glass flying in all directions.

I'm glad he didn't try. As a 15yo my teen friend and I spent half a summer grinding a 6" mirror.

Then we were told to Foucault-test the mirror. We couldn't understand the included instructions. We lived in the middle of nowhere, noone to ask, internet didn't exist, library had bupkis. If we had figured it out, we'd still have had to mail it somewhere to be aluminized. End of story.

Few people make their own ICs anymore either.

Yes. Not sure what about this justifies the oohs and ahs.