The ninja is a sportsbike, not a cruiser so of course it has a high end redline. They are meant to be driven that way. The difference between a sportsbike and a cruiser is actually pretty extreme. I can hit 100km/h (65mph?) in 2nd gear at 9000 rpm. I redline at 13.5k And that's on a detuned inline 4. Honda599 has said that he'll hit 100km/h at redline in 1st, just imagine what a full blown cbr could do?
The size of the engine is not always an indication of how much power you have at your command. I can take 3rd gear from 30km/h to 120km/h by twisting smoothly twisting my wrist. Engine isn't even starting to struggle at that point. Difference between gears is the amount of vibration, and towards the very top end my ability to accelerate falls off. There's no way my friends 800 marauder could do something like that. If he pushes close to redline in 3rd he'll hit 100km/h.
In order to get anywhere near what a sportsbike could do in a cruiser you need a massive engine. The rocket 3 could blow me out of the water, but I'm willing to bet that near to any 600cc sportsbike could take an 1100+ cruiser without a problem. So saying that you quickly outgrew a cruiser and needed a bigger one doesn't apply to the ninja. I could do everything on my hornet that you can on your meanie... though I might have more trouble holding a straight line as a result of a shorter wheelbase I can take corners a lot harder

It all becomes a question of cost vs benefit.
Of course I'm generalizing from a single example here, but everyone does that. At least I do.
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