This year's tax law allows Sammy to sell, but only to family members. These are spouses, ancestors, your and your spouse's descendants such as children and grandchildren, and their spouses. Still, these people probably know about Suzy. They may be willing to take the risk only if Sammy sells at a very low price. Suppose that three or four years down the road, Suzy and Sammy are getting along, but the business isn't.
Big competitors hit, or the market has shrunk, or the kids made bad credit decisions.
Finally, they have no choice. They shut down the business. Now, neither of the heirs who received business interests are active participants because there is nothing in which to participate. Taxes fall due at the worst times. The kids will have to pay them at the moment the company hits the wall.