Also, a backmarker two laps down in Monaco has all the reasons to race, specially this year. For Lutus, Virgin and Hispania, any point they pick is likely to mean 10th position and a lot of money at the end of the year. And if, as it is most likely, none picks a point, then the 10th position will go to whoever get a 11th position. And if not a 12th and so on.
In Monaco cars crash, so 2 laps down you are easily 20th, or 18th, or even 16th... what if later it starts to rain and more cars crash? This could be the race deciding the team's classification at the end of the year, and just staying in the race has a lot of value. If you are a Lotus 2 laps down, you want to run like hell to stay ahead of that Virgin 2 and a half laps down!