Everyone needs permission from the US government to remain in the US and to work in the US. US employment-based immigration laws govern who and how one can obtain work permission, i.e., work visas. The ability to remain in the US and the ability to work in the US however are not necessarily entwined. Spouses of individuals who receive work visas are given visas that allow them to accompany the principal visa holder, i.e., the worker, but does not always allow them to work.
Spouses of E-1 (treaty trader), E-2 (treaty investors), E-3 (specialty occupation individuals who are citizens of Australia)...