1. Some works for government agencies, CIA, FBI, SEC, FDIC etc...
2. Some stays in business field, personally, I do not see anything wrong with that, some people just don't like to practice law, so what.
For some people, joining a large firm might not be their top choice.
For example, I have received offers from large-medium size firms, but ended up working for a large corporation. Besides salaries, there are other factors to consider, location, benefit, and profit sharing. The job I took pays 1/3 less than what's been offered by law firms, but I get a lot of vacation time, excellent benefit and retirement package, and...I only work 40 hrs per week. However, I guess working for the legal dept of a corporation is still considered staying in legal field.