This is not true. Giants like Apple, Google and Microsoft get sued all the time. They face hundreds of troll lawsuits at any given time.
http://arstechnica.com/tech-policy/2014/02/apple-top-target-...
Mentions Google, Apple and Samsung (respectively 192, 191, 151 lawsuits over last 5 years). Microsoft has mentioned similar numbers, but I can't find a reference off hand. Google for "patent trolls target Microsoft"
This is not true. Giants like Apple, Google and Microsoft get sued all the time. They face hundreds of troll lawsuits at any given time.