12 hp instead of 15 hp

I’m just thinking if I should get a 125-er chopper for cruising. With my driver’s license from 1977 that’s possible. What’s surprising now is that most of the newer machines have only 12 or 11 hp instead of the allowed 15 hp. Why do you give up 20 percent of the power on the part of the manufacturer? And with the weight of the machines (sometimes over 3 talents) + driver (2 talents) it looks like a lot like a torture for the engine. – so please don’t be upset if my question for experienced bikers may be completely wrong!