The difference is McDonalds haven't patented "a circular ground meat disc 1-2 cm thick on a similarly shaped bun with high fructose and vinegar sauces and a token minimum of vegetables, including lettuce, pickles and tomato". I think the point is you should only be able to sue against profit a company makes, and damages against current businesses are desirable because it shows someone competing.

To simplify everything all patents should last 5 years max.