It's kind of like those sites who want journalists to write for them for "exposure" (or ask photogs to use their photos, or artists to use their art, etc. without paying)-- sure, maybe millions more eyeballs see your writing, but you're making nothing off of it and just hoping you'll get something down the road. Meanwhile, the smart writers are taking gigs that maybe only a few thousand will read but they will get paid reasonable rates (and sometimes very good money) every time.
Not to say that many B2B publishers won't participate, but it'll be at a smaller scale and, I think, always with an eye on the trade-offs, which, again, aren't so great right now.