A lot of people in my country get denied disability benefits who genuinely need it, and then have a long fight to receive support. Or they are like me, and give up entirely, because it is easier than to go through the system. So I agree with most of the above. It's called knowing how to play the system, when you fake some kind of disability, and it's wrong.
I'm not sure it's all caused by people who are faking though. I think it is caused by a system that starts out with thinking no one is really entitled to care or financial support from their government. The fakers are just the scapegoats that some people use to blame when those in genuine need are denied what they are entitled to. Maybe it is different where you are from? It seems to work different from country to country.
I still cannot spot fakers here and assume they are a rarity, and I've never met anyone in real life who has claimed to have PTSD. I sometimes get confused when people say it is a trendy illness, but then I don't always engage enough with the mainstream media to know these things.