If one is actually serious in bringing senior engineers in house under part time work hours, why would one make assumptions to limit the scope of who would find

If one is actually serious in bringing senior engineers in house under part time work hours, why would one make assumptions to limit the scope of who would find it acceptable conditions to come in under? In the US one could offer comp for health insurance equivalent partial value, or go the other way and carry full health insurance with the part time salary reducing. Or maybe this whole situation favors a setup in nations w/ universal healthcare.