Why? Well, I although I haven't read them all (I skipped the historical ones) they offer so much and you gain something new each time. The various aspects of human nature and the rich, glorious language that has become absorbed into our everyday speech are amazing.
Sadly, I think many people were put off at school by being forced into covering a text in a way that made it inaccessible and I know that I have a personal dislike of Twelfth Night due to the way it was pushed into an unwilling brain at "O" level. (See, I'm that old!)
However, despite that I persisted and adore Much Ado, and that was before seeing it at the Globe and then David Tennant (honest!), and I particularly love the tragedies...Hamlet and Anthony and Cleopatra. It is wonderful to see them being performed but you can still get so much from reading them.
Friends think I'm weird, but I just think they're missing out.