Well, they (at least many of them -- e.g. Microsoft, Apple, etc) also 'play the game' with their own patents, so it's not out of character for them to use patents offensively. By using their patents offensively, they are contributing to the situation where they are required to 'foot the bill' with their own liabilities, at least. If they adopted a less aggressive stance, and instead put the money they've spent on lawyers towards lobbying for patent reform, what they 'need' to do to limit their liability might be really different.