Big trade shows under one roof are kinda strange in today's media and advertisement landscape. Youtube is the biggest trade show in human history and it's free and available 24/7. And if you showcase your product there, you don't even have to compete with a warehouse full of other stuff all coming out at the exact same time.
I can see NAMM being beneficial to tiny companies without much reach in the market because it's a place where all the media is concentrated, so you could get a shot at more exposure if you release your product there, but as for big companies who already have a following and can reach their audience and market any time they want either way? Seems pointless for those guys to spend a ton of money on booths and travel when they could just release something on their own social media sites.