A company that sues competitors for patent infringement is like a a defender who has been beaten so thoroughly that he turns to plead with the referee. You don't do that if you can still reach the ball, even if you genuinely believe you've been fouled. So a company threatening patent suits is a company in trouble.
Because there's so much scope for design in software, a successful application tends to be way more than the sum of its patents. What protects little companies from being copied by bigger competitors is not just their patents, but the thousand little things the big company will get wrong if they try.
And on the topic of companies in business just to sue others he gets to the point that patent law exists not for some abstract purpose. Patent law exists for the greater economic good (by rewarding inventors with a chance to profit from their invention for a period of time we encourage people to invent). As he says:
The American way is to make money by creating wealth, not by suing people.