I think you nicely describe the planning part of marketing - but you have to include the execution where you reach out to your target market. Advertising (in all it's forms) is a crucial tool of marketing.
I've run into a few companies who have painfully put an 'advertising guy' in charge of their marketing department and it's not worked well (in my limited sample). People are often great at advertising but couldn't put a decent product strategy together to save their life (or job!).
You wouldn't put your web developer or icon designer in charge of system administration or database scaling, right? Just like non-coders tend to lump everything technical together as 'computer stuff', technical folks can fall into the trap of lumping accounting, marketing, advertising, etc. into the same batch as 'business stuff'. That path leads to madness.