I think you are misreading what he means.
Events like E3 and Gamescom get massive media coverage, the kind that penetrates past even typical gaming sites and appeals to folks who don't even own these systems. You want to put the products out there that sell and draw attention - and unfortunately the Vita ain't it.
Like they could have spent 30 seconds talking about Freedom Wars on stage at Gamescom and announced a release date but what does that do for anyone? Instead you just post it in a blog update where most folks who own Vitas are going to see it anyway.
Yep, it's all about the opportunity cost. Five minutes talking about Vita is five minutes not talking about PS4. And as good as the Vita is, it's clear it's not going to be a big money maker for the company the way the PS4 could be.