Those big companies depend heavily on their patent portfolios for both offensive and defensive uses. Once in a blue moon someone will win something like this, but most of the time their fancy big company lawyers will stave it off (and indeed, it sounds like they may avoid this liability because the patent they've infringed may be invalid), often by sheer legal force ("How are you going to afford to fight my army of $1k/hr lawyers?").

When it's business as usual, these companies rather enjoy the benefits of having large portfolios filled with patents of dubious validity. They don't want to get the ball rolling on something that may end up costing them money in the long run, like drawing attention to the dubious nature of most patents or starting an initiative that may backfire by invalidating some of their own IP.

You'll find this is common with big companies. The law governing a certain type of conduct may be a totally incomprehensible, unpredictable, and uneven disaster, but incumbent players don't mind because for the most part, it enables them to scare off any upstart challenger by intimidation. The challengers who are too foolish to back down will generally struggle to keep representation and eventually end up completely destroyed (see Facebook v. Power Ventures), which makes a fine example to warn off any other cheeky upstarts who think they'll play hardball with the big conglomerate.
These big companies know that their peers won't press the legal matters or try to get the law improved because they benefit from the same effects. Instead, two big companies with beef will, after some legal posturing, eventually come to a mutual licensing deal (which may be in the form of a settlement) where they each send the other a large check every month to license the patents that could be construed as covering components of each others' products.

The matter is only pressed when there's no mutually-beneficial agreement to be had, like in Oracle v. Google regarding the Java API; Google wants the right to re-implement the Java API as they see fit, without having to pay royalties, and Oracle wants the right to exact payment from anyone implementing the Java API. Indeed, some Sun insiders consider Google's refusal to license Java components (they had apparently been in talks at some point) as one of the final blows that forced Sun to sell.

However, the way that that intellectual property law is written, it's difficult to have firm, universally-applicable precedents established. Fair use is fundamentally a case-by-case basis, which means even if Google gets it established that their use of the Java API is fair (afaik, it has already been established that APIs are protected under copyright, so fair use is the applicable defense), it doesn't necessarily apply to anyone or anything else. That means big companies can still intimidate little guys by threatening to drag them through 10 years of ultra-expensive court proceedings, plus the risk of a judgment finding damages, injunctions, etc., if they don't immediately comply with the BigCo's demands.

Convoluted and murky law benefits the massive corporations, who would much rather pay lawyers a few million to dispose of a plucky competitor than actually have to fight that competitor in the marketplace.