There are perks to an LLM, however those perks accrue to a very small number of students. Foreign attorneys, scholars, and tax lawyers might all benefit from an LLM assuming that it's obtained from a top law school (think NYU for tax law, etc).
Many students who graduate from non-elite law schools wrongly believe that an LLM from a more prestigious institution will give them an edge in the private sector. If they can get into a top ranked program, perhaps. An LLM from a tier 2-3, however, is probably a waste of money for the vast majority of students. I know a guy who got his JD at Loyola-New Orleans, his LLM at Duke, and was hired as a professor. I think his situation is the exception rather than the rule.