But is not that the point?Dark Sun is low-magic enough that people finding out you're a wizard could lead directly to your death at the hands of essentially a mob of peasants wielding crummy stone pitchforks. Clerics and druids are less unpopular but some of the stigma surely still attaches, especially given the reputation of the templars.
The sorcerer kings are above that sort of persecution, and in order to make the setting work economically a DM actually has to either raise the magic level enough to let them grow more food per square mile, or stretch out the geography by a factor of 10 or more (100+ times more prime farmland per city-state). But Dark Sun as written is low-magic, high-mysticism (via psionics).
That Dark Sun is (one of) the Anti-D&D setting.