Currently, dependents for most types of foreign skilled worker visas are not allowed to be employed in the US. This makes it very tough on families to come to the US with their skills. Instead, many choose not to bring their highly valued skills to this country, or simply leave.
Those people then use their skills to compete with the US and earn their high salaries, create jobs around them, and spend their earnings in a foreign country, and pay taxes to foreign countries.
Why not help the US economy by allowing more highly paid jobs to stay in the US (and create additional tax revenue & spending in local US economies) by allowing those families to work?