Buying each other's products only gives you what's actually made it to market. Plug-fests are full of unreleased stuff. (Buying each other's stuff, to tear it down for competitive analysis, is exceedingly common. But you don't do that at a plugfest.)
Trivia: Plug-fests used to be called Bake-offs, but Pillsbury sued to stop it: https://www.cs.columbia.edu/sip/sipit/pillsbury.html
Trivia 2: Bluetooth calls theirs an "unplugfest". https://www.bluetooth.com/bluetooth-resources/unplugfest-eve...