There are so many reasons why . . . I don't think I can name them all.
Smuggling or illegal goods/people
Trafficing of illegal goods
Murder
Grand Theft Spacecraft
Speeding
Illegal business practices (i.e. Enron, Martha Stewert)
Basically just go down the penal code and have fun with it:
Here it is for the Republic of California
http://caselaw.lp.findlaw.com/cacodes/pen.html
Look for Title 8 & 9 for some more notorious crimes
TITLE 8. OF CRIMES AGAINST THE PERSON
CHAPTER 1. HOMICIDE ............................................. 187-199
CHAPTER 2. MAYHEM ............................................. 203-206.1
CHAPTER 3. KIDNAPPING ........................................... 207-210
CHAPTER 3.5. HOSTAGES ............................................ 210.5
CHAPTER 4. ROBBERY .............................................. 211-215
CHAPTER 5. ATTEMPTS TO KILL ................................. 217.1-219.3
CHAPTER 6. ASSAULTS WITH INTENT TO COMMIT FELONY, OTHER THAN
ASSAULTS WITH INTENT TO MURDER ....................... 220-222
CHAPTER 8. FALSE IMPRISONMENT ................................... 236-237
CHAPTER 9. ASSAULT AND BATTERY .................................. 240-248
TITLE 9. OF CRIMES AGAINST THE PERSON INVOLVING SEXUAL
ASSAULT, AND CRIMES AGAINST PUBLIC DECENCY AND GOOD
MORALS
CHAPTER 1. RAPE, ABDUCTION, CARNAL ABUSE OF CHILDREN, AND
SEDUCTION ............................................ 261-269
CHAPTER 2. ABANDONMENT AND NEGLECT OF CHILDREN ............... 270-273.75
CHAPTER 2.5. SPOUSAL ABUSERS ............................... 273.8-273.88
CHAPTER 4. CHILD ABDUCTION ...................................... 277-280