Firing people is risky for the person potentially being fired, not for the owners of the firm. Growing and shrinking over time is part and parcel of running a consultancy. That's why you see it all the time, and I'll bet if you look closer at the ownership during layoffs you'll find that they very rarely miss a paycheck and usually escape unharmed.

The fact that it's an unpleasant reality doesn't make it any more risky than e.g. having to pay taxes.