Hmm good question. Probably a combination of inherently stressful work, long hours, difficult/emotional/angry clients (depends on what area of law you are practicing, but people often need an attorney only when going through a negative experience like an arrest, divorce, injury, etc.), the high cost of a mistake, exhaustion or toll from the "content conflict" naturally found in some areas of a law, and the pressure of billable hours. One thing they don't discuss much in law school is the importance of billing clients. There are times I feel more like a salesperson than a lawyer. Of course this can be avoided if you work for the government or other public interest law.
The job market in this country is very strong right now and it's my understanding that includes the legal field. Hopefully it lasts for the foreseeable future! That being said, one thing that impacts the legal job market in Chicago is that there are 9 law schools in the state of Illinois and supposedly new JDs regularly move to Chicago after graduating from law schools located in neighboring states. So I have heard that this state is a bit more saturated with licensed attorneys than most other states. For what it's worth, I recently read that the top areas to enter right now are IT law, Healthcare law, Corporate law, and Complex litigation.