Why do most book clubs read the classics?

So my question is: why do most book clubs these days read the classics?
Maybe book clubs read the classics because it’s good to have this “cultured knowledge” or maybe because the average person needs a little help from peers to fully understand the book? I know I’ve cracked open Pride and Prejudice more than one while lying in bed before going to sleep, and I couldn’t seem to concentrate hard enough to sift through the “older” English and follow all the Ms Bennets.