A: Because they get other jobs that meet their income requirements.
People who make it through law school usually aren't idiots. So if they fail to achieve a satisfactory career in Law, they move into other areas. Attorneys work in government as political appointees, lobbyists and policy people; they work as corporate managers; they run businesses in areas other than law, etc.
Also consider that the barriers of entry for lawyers are high. Referrals are a huge source of business, so it's difficult to start a new firm without alot of capital.
People who make it through law school usually aren't idiots. So if they fail to achieve a satisfactory career in Law, they move into other areas. Attorneys work in government as political appointees, lobbyists and policy people; they work as corporate managers; they run businesses in areas other than law, etc.
Also consider that the barriers of entry for lawyers are high. Referrals are a huge source of business, so it's difficult to start a new firm without alot of capital.