well, the 'average population' is a bunch of obese sedentary people.
and the US RDA for protein is the 'bare ass minimum to keep you a moderately healthy, obese, sedentary person'.
Also, for fat loss, many people find that lowering carb intake helps, but that causes a large calorie drop, and dropping too lower puts you in starvation mode which is not great for fat loss. So, you make up for those calories with protien and fat.
another group of people that can have protein issues: vegans and vegetarians. animal proteins are complete, plant proteins are not, and can lead to deficiencies. I personally don't feel soy is a smart protein source...way too much conflicting data out there, and way too many people seem to get upset stomachs, gassy, bloated, from taking in soy in more than very small quantities.