Why metric lathes don't use a threading dial

Single point threading on a lathe is this magical dance between man and machine, except when it isn't.

I found this video to give the best explanation, with the math to back it up.

It turns out it is because inch threads are defined as threads per inch and metric threads are defined as mm per thread. and mm per thread does not give the ratio advantage that allows for a simple indicator on when to engage and disengage.