This table is an ISO recommendation defined by a committee of experts.
As always for such recommendations, the value have been chosen to be safe in the worst case, i.e. worst case for tire construction, for tire pressure, for tire load... + a safety margin.
If you follow these recommendations, you are sure to be safe, if you are infringing them, you may have safety issues or not, its your own risk.
The fact that you do not experience problems while infringing the recommendation is not a proof that these recommendation are wrong, only that you are not in a worst case condition.