Seems like most responses here are from the perspective of freelancers or remote contractors. Through that lens I can see being skeptical of design tasks - specifically ones that have you work within the same field of the employer (ie: a health insurance company asking you to design a plan selection page).

When it comes to full-time gigs, however, you'd be hard-pressed to find a potential employer who doesn't require a take-home design task, a whiteboarding session, or both. For better or worse it's SOP at this point, so you might as well get used to it.