I ask myself—who would use a knock sensor in daily use, and why? They are used in OEM cars destined for unknown fuels and conditions with careless drivers. When they work, they reduce power and efficiency much more to stop det, than a well-tuned system that does not knock. They invite people to run crappy tunes or crappy fuel, because "the knock sensor will save it".
If you are running greater power, you also need to use greater care, as you are closer to bad things happening. The bottom-line is that you could tune your engine correctly, make more power and MPG, and have higher reliability by tuning it, than developing and tuning a knock sensor to work reliably on your specific engine. It's like taking the time to get a girlfriend that won't cheat on you, or a girlfriend that will text you if she's bangin' someone else.
I'll work for the first one, but hey, that's me.
Exactly my point, that if you're worried about knock, you have a poor tune, or maybe have encountered some questionable fuel. I can see the point of it, if the latter is the case, because we can't always know the quality of the fuel entering the tank. So even then it is more of a safety device than a crutch.
For all the crap I might give Honda for doing the system on my bike the way they did, I have to give credit to them for pulling over 150HP per liter from that little engine, running a turbo up to 19+ PSI boost without an intercooler, and doing that on pump grade fuel... with 1980's tech. They actually de-tuned it for production, reducing boost about 4 PSI so it would survive on pump gas. Its '83 650T brother bumped HP another 15 or so, while also reducing boost from 19 to 16. I don't think there is another 'stock' bike that can pull ahead of the 650T from 65MPH to 140MPH in top gear roll-on. And still, no knock sensors to be found.
Still, like I said, I can see the point in knock sense if it is used solely for the safety factor, and not abused to coax more power from the engine than would otherwise be practical given the engine design and state of tune.
As for the girlfriend analogy... I'm on the fence with that one. You shouldn't have to work for a girlfriend that won't cheat on you. Not cheating should be a given. If she cheats and tweets, well, at least she's being honest. And then, if she's cheating, I'd be looking at myself... after shoving her down the road. At least with tuning the engine, you have control over the vast majority of variables.