Those possibilities all make sense at the individual level (I've had personal experience of several) but at the macro level the correlation with economic performance seems pretty tight. I'm having trouble buying the idea that negative reasons have taken over the trend. Nor do I think the uptick is especially small, it looks entirely proportional to me (bearing in mind that unemployment is a lagging indicator, and the financial crisis began in 08.

I hate my job more than anything I've ever hated. Every morning when I wake up I try to figure out if today will be the day that I call in and tell my manager that I can't do this to myself anymore.

My therapist keeps begging me to quit. Ultimately I'm just too afraid of not finding anything else to quit without a new job.

I guess it is nice to know that I am not alone.