Simple enough. When a company ceases trading, nobody expects the people who bought their office equipment to honour outstanding warranties, or even the people who bought out the lease on the building they traded from. If another company buys the design of their products and continues making them, that doesn't oblige them to honour warranties for the products they didn't make.

This is exactly the same thing, except it was the company name that was sold. Acme Corporation sold the Acme brand to RoadRunner Inc, then quietly ceased trading taking all their liabilities with them.