Marketing?

Well, this book writing thing may not turn out to be like I thought it would be. I visualized digging out my old typewriter, buying me a pipe and jacket with leather patches on the elbows, some reading glasses with a string tied to the earpieces and me just standing,  looking off into the distance through the window in my study (Oh yeah, I'd have to build a study), holding my pipe and doing a lot of thinking. Now I'm being told I need a special Facebook page, get on Twitter, get a blog and some other things I never heard of to build myself a platform to get my name out there for marketing reasons.....What in the heck does marketing have to do with writing a book?