"Pourquoi boit-il autant de bière ?"
Shouldn't it be "Pourquoi boit-il TANT de bière ?" ? Because there is no comparison with anything else.
This sentence in English is awkward without the rest of the comparison. I would say something like " Why does he drink as much beer as his friend?" or "Why does he drink as much beer as he can tolerate?" Seems like the equivalent in English would be closer to "Why does he drink that much beer?"