What makes this even newsworthy--if anything does--is that normally you don't think about postdocs buying things for the lab. They're just the worker bees. So wouldn't it be better to pitch the principal investigators instead?
We should note that this was a postdoc event hosted by Penn's Postdoctoral Biomedical Council; it's not that a bunch of lab equipment vendors got together and said, "Let's try to sell stuff to postdocs." The event was a fundraiser; I'm not sure how, but presumably the 20 vendors who displayed their wares paid booth fees. This year's take wasn't yet tallied when the article was written, but at least year's show--this isn't the very first--they raised about $15,000. Proceeds will go to support postdoc research, the article says.
What's behind the idea of staging an equipment show for postdocs? With postdoc positions becoming longer--and postdocs therefore becoming more experienced on average--they're particpiating more in running the lab and in making purchasing decisions. "Postdocs do a vast amount of ordering for a lot of their labs at Penn, so they're able to better see what's available," fundraising committee chair and postdoctoral fellow Todd Waldron said, quoted in the article. It's implied, I think, that PIs don't know their way around the lab so well anymore. If you'd like to sell something to established PIs you'd be better off selling grant writing services or something more closely related to how they spend their workdays.
This wasn't mentioned in the article, but there's another reason for laboratory vendors to try to sell things to postdocs: A few will soon be setting up their own independent labs, spending startup funds that range into seven figures.