People don't necessarily choose not to work. Some people are retired.
Retiring is choosing not to work.
Some are stay at home parents.
Could stay at home parents choose to work outside the home and cart the kids off to Nancy Pelosi's taxpayer funded daycare?
Some are in prison.
Don't many people work in prison?
Some are disabled.
Until I found out about double and triple dippers, I didn't realize you could collect several kinds of disability and still hold a full time job.
Some are actively seeking employment but cannot find it.
We still have immigrants coming into the country filling jobs. Perhaps you mean, people can't find jobs that suit their standards.
Some are independently wealthy.
That's a choice not to work as well just like retirement. Perhaps that's one of the rare cases where capitalism produces a malincentive to work.