Defrauding Medicare

One thing I do not understand is why people try and rip off Medicare.  I understand Medicare may not be the best program the government has but I still just do not understand why people rip off the government and why they take advantage of it.  I was reading in the USA Today newspaper from Friday October 5th 2012 that 91 people where charged with defrauding Medicare of $429 Million dollars in 7 cities.  They had a federal strike and arrested a hospital president, doctors and nurses for frauding the Medicare system by submitting false billings.  I think this is so wrong and very unnerving because people like those 91 people who rip off the system are hurting us debt wise, and they are taking away funds that could be used to help someone else who is actually sick and could actually use the money.