Gross part is that you are boiling same liquid in open space where people are working and making a mess. Also you are going to accumulate residue ar the bottom.
Unlike meat or vegetables this can't be washed.
And what's to wash? You don't wash food after cooking, and pasta is like bread -- it certainly doesn't need washing beforehand either. It's just flour and some other ingredients.
It's not like vegetables where you need to wash off dirt, pesticides, etc. Or meat where you wash off bacteria. Those aren't issues with pasta.
Just from a food safety perspective I'm not sure it's legal to reuse across days, given that it's going to take all night to cool, only just in time to be reheated again.
If there was a way to get rid of the insect eggs people would presumably want to do it too, but iirc they're just too small to filter out.