I think the massive salary drop off will make the late-career transition from engineering to law hard to stomach. Someone in their 40s or 50s with 20-30 years of engineering experience probably has a family, is thinking about their retirement plans, and is commanding the salary of a senior engineer (at least). Very few people are going to be willing to take 3 years off from work to go back to school only to spend another few years as a junior associate making far less than they could as a senior engineer. A lawyer going into policy or any other altruistic area of the law should expect an even larger salary gap.