There definitely are people that get disability income, yet are quite capable of working but choose not to, so this doctor has a point.
I have an acquaintance who got disability income due to some mental symptoms, and continues to claim for it. Yet although this person said they were not capable of working, they were quite capable of starting a family, using their disability income as funding for this.
Not that I am against people not wanting to work. The employment rate in countries like the US, UK, Canada and Australia is very high: around 70%, compared to an employment rate of around 60% or less for countries like Italy, Spain, Mexico, Greece, and Ireland.