Welcome to the forum.

The simple answer is because that's how Honda designed them. The more rake, the more the bike tends to go straight without steering input, but requires more steering input to turn it. Sport bikes turn more readily because of less rake, and the "Long Fork Choppers" need half a block to turn around.

Having grown accustomed to the Rebel, when I test rode a sport bike, the steering felt "twitchy". It took much less steering input to turn the bike.

 

The (250) Rebel has a 30º rake, even the newer 300/500 models have the same measurement although it's 28º in the frame and an extra 2º in the trees. I've never found anything solid about the 450 geometry but I would guess it's pretty close to the 250 dimensions.

Of noteworthy relevance: the rake is not what defines the handling characteristics, ultimately it's the trail dimension. Sure, rake influences the trail but in the end the triple tree design can offset any amount of rake. In other words you can have a stock 35º rake in the frame and +5 raked trees add another 5º but the trail is shorter than stock. Triple tree offset (distance of forks from steering stem) defines the trail so you can increase or decrease trail with stock rake trees as well. In other words you can have sportbike-like handling characteristics or wheelbarrow-like handling characteristics depending on how you design a chopper...in this regard "stupidity" becomes relative.

In the end it's all give and take. More trail yields high speed stability while reducing steering response, and less trail yields more steering response while reducing stability at higher speeds (which is why a lot of sportbikers add steering dampeners).