michaelporteous,
As Jimmy do Little has already said - there is much more to it than meets the eye. If you obsess over every little detail - why cant we do this, why dont we do that - we would never leave our homes, let alone go flying.
The simple answer for intersection take offs are that;
It saves time, fuel aka Money.
Can help ATC when they're busy - more movements.
Performance calculated to ensure that at V1 (just prior!) you can reject and stop. Or continue and reach the minimum screen height.
There are many other performance based issues here too.
These procedures are being used world-wide everyday and are tried and tested otherwise we wouldnt be doing them.