How many people are getting 150g of real bioavailabile protein every day?

Yes, so if you add ~20g of protein to your diet with protein powder, and skip a meal that would have provided you with ~20g of protein but also would have included carbs and fats, the net result is that you are cutting curbs and fats.

I'm not sure what point you're trying to make here.

Dosage depends on the size of the person, there is no flat number. For people who lift with the intention of gaining muscle size, there's is a positive trend of additional hypertrophy that starts to flatten out at around 1,6g/kg.

Not only is it discarded, it's actually bad for the body to have to piss this out constantly.

If your pee is foamy, you're eating way too much protein!!!