At the high end, the typical CxO golden parachute that can be equivalent to several years of pay. At the low end, additional stock options or bonuses at the time of signing.

Either way, an incoming CxO has a lot more negotiating leverage (and usually experience) to ask for such things than fresh graduate looking for his first job. Low wage employees usually have no negotiating leverage at all and must accept the contract as-is or remain jobless.

Edit: I'm definitely not against banning non-competes for everyone. But a candidate for a C-level executive position is much more likely to have the resources and the knowledge to negotiate fair concessions or compensation for accepting a non-compete.