Well, I work in an insurance company, translating disability files in the claims area. A rough guestimate places the psychiatric files at roughly 60% of all claims. The next largest percentage is musculoskeletal (in particular back pain, etc.) and the smallest percentage is for all other combined disabilities (heart, stroke, high-risk pregnancies, etc.)
Let me try to explain in lay terms, since I am not a medic. Psychiatric claims come in a variety of shapes and colours so to speak. Very few are really psychotic problems, ie, where the patient has hallucinations and/or is delusional. The majority are people who have burnout, (and I agree - one week does not cure it) - usually the result of an excessive workload, combined with perfectionism, inability to say "no", etc. The others can be anything from reactive depression, adjustment disorders, behavioural problems, personality disorders, and of course major depression etc. etc. All of these can make an individual non-functional for periods varying in length.
First of all, I think in today's world, at least in Canada, there is a lot less stigma attached to being open about this condition than there was even 20 years ago. It is being treated like an illness. Period. People go for help, even if it is "only" a need to learn to cope.
Secondly, I think there is some sense of entitlement (at least where insurance is concerned).
That having been said, it can be successfully treated, but it usually does take several months AFAIK