WCPM or Lexile Levels: The lesser of two evils?

This post has the potential to be draft one of a long-winded book about teaching, since I now teach a full-inclusion fourth grade class at a new school site, but I'll spare my plethora of readers (joke), and stay focused on the most pressing questions swimming around in my head:

Quantitative Speed vs. Quantitative Readability

I'm now teaching in a school district that doesn't base student worth (ahem, I mean ability) on the speed and accuracy of leveled reading passages. But it's a trade off for Lexile leveling- something my former reading teacher self had little knowledge about before entering a new district with different assessment priorities.  

My new district uses the Lexile Framework for Reading as a quantitative assessment of both students' reading levels and texts' complexity. Students receive a Lexile measure from certain reading tests. Books and other texts receive a Lexile measure from a software tool, the Lexile Analyzer, which evaluates word frequency and sentence length. Many schools use Lexile measures to assess students' reading levels and match students with appropriately rigorous reading material.

As a teacher, I find such information helpful when determining my students' reading ability and what books might fit them. What concerns me is that in many situations, Lexile measures become the primary factor in book choice and recommendation, and in my case, an important facet of measuring student ability on the report card. Lexile levels organize our school library, and many classroom shelves. Students in my school are encouraged to find books within their numbers. 

While identifying readability can be useful when evaluating textbooks, guided reading texts, or other teaching materials, selecting books for classroom instruction and recommending books for independent reading should stand alone.  Bottom line: Exclusive reliance on reading level systems limits readers. Bookstores, libraries, and home bookshelves aren't leveled. Is this practice valued because it's better for kids or just easier for adults? 

"Your Grace, I feel I've been remiss in my duties. I've given you meat and wine and music, but I haven’t shown you the hospitality you deserve."

-Lord Walder, Game of Thrones (1125L)