Thing is, I wouldn't deny that Ion/Impulse threads have a lot going for them, almost entirely on the engineering side. There's a few things going against them as well.
First off, SP never gave them an actual name until fairly recently. When they brought out the Impulse, if they'd called them "Smart Threads", they could have easily carried that name on them forever. A name may not be a technical issue or concern, but if you name an item something stupid, it's not likely to thrive.
Second, really, nobody other than Smart Parts and its sub-companies jumped on board. Even there, some of the nicer Shockers ran Cocker threads. So Impulse threads are found on the Impulse, Ion family, and Luxe. Even the popularity of the Luxe hasn't given a huge rise to the Impulse threads. Meanwhile, every other high end gun, and most of the mid-range guns, on the market? Cocker threads.
Third, there's still a Smart Parts stigma out there. OK, they were assholes about how they did business. A bunch of people around that same time frame were, but nobody remembers that. Granted, I don't think the Gardners were smart (haha) about how they pursued what they wanted. They essentially guaranteed the player base would hate them. What they really needed back then was a better PR department, but it is what it is. To this day, people will still make a face when someone brings up Smart Parts... to the point where it was genuinely shocking (I'm on a roll) that they'd dip back into that memory well with Shocker Paintball being SP.
Finally, the best thing on the player side of things for Impulse threads is that it doesn't take three weeks to turn a barrel onto or off of a gun. Simon's brilliant short Cocker threads, picked up by Planet Eclipse and Empire, have solved that problem.
That's just one idiot's opinion, though.