Why Don't People Work ?

While the current economic situation will certainly cause the "unable to find a job" category to increase (maybe even double), I found the statistics about why people do not work interesting. The second graph shows the percentage of people over 65 who still work, and I would imagine that the reason for that has a much different demographic. I find it encouraging that in general, people who want to work, for the most part can - in normal times, and tragic that so many senior citizens must work for day to day sustenance.

Why are so many people older than 15 not in the work force today? According to a 2004 study (current unemployment will change these numbers temporarily) the main reasons are:

37.9% are retired
19.1% are going to school
14.7% suffer from chronic illness or disability
13.2% are taking care of children/others at home
4.3% are unable to find work
3.6% are uninterested in working