[pete]

if you were to move the pegs rearwards...
when standing you are now leaning foward
carrying a lot of your body weight on your arms
and a very heavy front end.... so you put higher handle
bars on to stop this... then your weight is rearwards
giving a light front end..that will want to slide around..
And while seated your feet/legs are under you more like a
sports road bike making it harder to keep your weight above
the bikes centre line while cornering seated on lose ground.
and moving quickly from a seated to standing position becomes harder.

you have to remember a lot of things on a bike are a compimise..
as any bike is bought by riders of diffrent hights , arm & leg lengths

..