Very true.
Although if you're ready to take a risk it is still very feasible to work in Japan without any of those. For example, I know a friend who came to Japan, enrolled at a private language school, got his student visa from them, and then worked at nightclubs and bars, sometimes even teaching English, all without a proper visa or college degree. Personally, I've worked at a place that never asked about my visa. Another "under-the-table" job. Some places don't "officially" want those extra gaijins on the payroll........
Like I said, it is also risky. Working for someone illegally has its problems.
-There is nothing to stop your employers from not paying you! Believe me, it happens!