There aren't. The criteria are somewhat similar, but it's the process of having to go through two processes. Some doctors do charge for the additional paperwork. You are talking about people who probably do not have a strong income at the time, having to apply for and pay for two separate systems. The way I look at it is if one has some type of permanent disability, chances are it doesn't usually change. Having to go through both processes is sometimes burdensome and expensive.
On October 18th, 2012. See this statement in context.