There is rampant insider trading by people in our govt on both sides and people hooked up with good connection in the the industry.
Tell me it would be easy to not be tempted? You work for a big firm, your friend a different one. All you have to do at dinner out is say hey dude buy stock in company A. He says thanks brother you buy stock in company B. We will both lay low, not invest too much, also invest in some losers, and make out like bandits.
You slowly buy up a few hundred grand of stock and boom you make 30% when company merges 6 months later. In a way you wouldnt even feel like you are that much a criminal.