Why not write a 'proper' book?

I have been working on my novel - solidly working that is - for the last couple of weeks, and most people's reaction to it is the same:

Wow!  That's so cool!  What kind of book are you writing?

And  then, invariably:

Oh, that sounds...interesting.  But you're so intelligent!  Why don't you write a proper book?

And there my patience ends.

It's not that I don't get what they're saying.  I've a BA in English Literature and a Masters in Shakespeare - I love highbrow pretentious literature.  I just don't enjoy writing it.

Prose writing for me is escapism, pure and simple.  If I want to be deeply profound or pretend to be clever, I write poetry.  But prose, prose is fun!  It gives me the opportunity to focus solely on words and phrases and get them as luscious and mellowly precise as they can be.  I like making people smile and laugh more than anything else, and so each chapter gets sent out in a flurry of emails, letting my friends sigh over alpha heroes in exotic settings.

And besides, who says they're not proper books?!  In a romance novel character development has to be detailed, characters have to be loveable but flawed, and sex must drive the action forward without becoming a standard plot point.  Mills & Boon publish around 100 new titles in e-book format every month.

So yeah.  To those who ask me why I don't write a 'proper' novel - I am.