The US requires employers provide "Equal Opportunity" across races. Legal departments have interpreted this to mean "we will ask everyone about their race to collect data to prove we aren't racist"
Note that the tracking is desired because a seemingly neutral policy can still be illegal; the EEOC gives the following example:
> An employer has a "no-beard" rule, which disproportionately excludes African American men because they have a higher incidence of pseudofolliculitis barbae, an inflammatory skin condition caused by shaving. The employer must be able to demonstrate that beards affect job performance or safety. Also, there must be no alternatives to a strict "no-beard" rule that would meet the employer's business or safety needs.
Those forms (nearly?) always include a "prefer not to say" option.
It's better now, but it was quite common for forms to permit only one selection and have no "Other". Having to repeated explain the existence of multiracial people to admins and H.R. types was...tiresome.
Note that the tracking is desired because a seemingly neutral policy can still be illegal; the EEOC gives the following example:
> An employer has a "no-beard" rule, which disproportionately excludes African American men because they have a higher incidence of pseudofolliculitis barbae, an inflammatory skin condition caused by shaving. The employer must be able to demonstrate that beards affect job performance or safety. Also, there must be no alternatives to a strict "no-beard" rule that would meet the employer's business or safety needs.
Those forms (nearly?) always include a "prefer not to say" option.