Forking crazy

I'm not JD, but both my race bikes have forks that extend above the tree. On a race bike it's desirable to be able to drop the front end, which effectively decreases the rake angle and speeds up steering response. Also nice for making adjustments to the front/back weight bias. Typically on a smaller race bike you add larger forks...they are usually longer too...this allows you to raise the front to correct geometry changed when you do things like change the rear swingarm angle. I like a good bit of down angle on the swingarm, this raises the rear end a bit...depending on how the front feels I might want to raise the front to level things back out...or leave the front down to put more weight up there and speed up steering. Just a nice option to have if you need it.
JohnnyB

Most of the vintage bikes have a pretty large rake...30+ degrees in most cases...while most modern sport bikes are down around 25 degrees. Rake works with trail though...you can get away with less rake if you have more trail, etc.
In most cases it's not going to make a difference on a street vintage bike...other aspects of the design will probably have a more detrimental effect on handling than the steering angle. Inferior suspension/frame, heavy wheels/brakes, high center of gravity, vintage profile tires etc.
I'd say certainly not worth altering the rake on a street bike...much better ways to spend the time and money, light weight bits, reworked forks, alloy wheels etc.
JohnnyB