I find it difficult to talk about my process while I'm writing because I'm still figuring it out as I go, For me, part of the fun of writing is discovering ideas in my subconscious. When I see the full picture, the near-finished or finished product, then I can retrace my steps and tell you how I came up with it.
The problem with that is, do I want to be talking about what I've written or writing something new? Often, I choose the latter.
I think the business side of writing is discussed so often at conventions precisely because promotion doesn't come naturally to people concerned with creating works of higher purpose (i.e. artists). In an ideal world, we'd all write from our hearts, our work would speak for itself and be recognized instantly by everyone we met. In this world, promotion is necessary.
A further comment on promotion:
I don't mind promotion on blogs. The most wide-ranging blog is about a person's life, and an artistic person (performer, writer, etc.) will want to talk about his accomplishments in the field. If there's a time and place for everything, a blog is the place for promotion. For me, the major appeal of reading a blog is getting to know the blogger on a more personal level.
A comment on Dave's reply, more to do with hearing other writers' creative processes:
Often I don't want to hear too much about what was going through the writer's mind when... Once the words are on the page, they should be open to some interpretation. If a reader wants to think about a passage one way, the author's actual thought process shouldn't interfere. This is why it bothers me to see Parker's life blurring with Spenser's (e.g. when he brought Pearl into the books, started naming characters after his wife...)
I don't like to pin creativity down to abstract principles (not that you do). I think settling into any rigid routine--ala Robert Parker's ten finished pages a day--is detrimental to creativity. I prefer something along the lines of an outline/sketch that I'm free to break from and adjust once the characters become more independent.
I do believe imagination and writing skills need daily workouts, just as you would eat right and exercise to maintain/improve your overall health. If we can make these tasks more voluntary they seem less like drudgery, and that's the goal: to create space for creative thinking.
And a comment on writing vs. selling, art vs. marketing:
Because creative writing is subjective by nature, everyone reacts differently to talk about the writing process. As you said, there are some blogs more about process than sales. If you want to read about process, read those blogs and not the ones about sales. It's much easier to ignore a blog about promotion than to ignore a writer shoving his book in your face and giving you the hard sell.