Well, I think the reasoning is that how you write currently is nothing like you'll need to write as a lawyer. My sister went to Harvard law, and was great at writing as an english major, but she said it's totally different in the legal world. Of course you need great basics, which they want to see with the sample, but I don't think it merits a a significant portion of your score.
And I say this from the someone who would have benefited from having the sample scored. I just think that by the nature of the huge #'s of people wanting to be lawyers (or at least go to school), they have to have a somewhat efficient way of sorting out people, that also tests critical reasoning and time pressure management. That is the why the LSAT format is as it is, and why LR is 52% of the test. In any rate, the correlation between LSAT and 1st year law school success is high enough that law schools and LSAC don't really feel the need to change it that much.
What irks me is that they don't grade the FREAKING WRITING SAMPLE and then have law profs complain about how we're all crappy writers.
I completely agree. I don't understand why the one portion of the test that truly demonstrates our logical reasoning skills (as opposed to our eliminate the options skills) is basically worthless. My clients aren't going to ask me A,B,C,D... they're going to want an opinion and a well-reasoned explanation of what I'm thinking. It what they'll be paying me for...