They'll have a mediocre LSAT score, but say "School X will let me in!". School X is terrible. They have lousy employment prospects, and charge $50,000 a year.
When you add miscellaneous fees and opportunity cost of not working, the law degree costs at least $250,000. And your school might close.
But (some) students still want to do it, despite the stark reality. As best I can tell, they don't see alternative options.
This group is shrinking however, which is why law school enrolments are in free fall. This chart from the LSAC shows a massive drop in LSATs administered.
http://www.lsac.org/lsacresources/data/lsats-administered
2008-2009 was the high water mark: 171,514 LSATs. 2014-15 likely will be less than 100,000.
Which is good. The industry's been in a bubble, and it needs to pop. But that means this is a VERY bad time to be going to law school unless you're extremely careful (and ideally have a guaranteed scholarship to a good school that won't close).