It's the stress of worrying about things happening, having to deal with the logistics of paying for it (paperwork, fighting with insurance companies, etc) while also dealing with the medical issue, and then after I've paid, worrying about it depleting my savings and possibly leaving me vulnerable if some other emergency happens. My emotional well-being is worth more to me than the extra salary..I just don't think extra money would have a more positive effect on quality of life than the added stress. And then if I lose my job, that's enough stress without worrying about losing my associated health insurance at the same time. I don't want to get pregnant and worry about whether the child will need expensive medical care throughout life. Etc. This may not be rational if you consider cold hard cash the most important thing in life, but I know that I would stress about these things.
I would also not want to deal with the stress of moving/paperwork of moving back when ill. Not to mention some medical emergencies simply can't be postponed 6 weeks, and these are often the expensive ones (surgery, etc). It also seems wrong to me to take advantage of the Canadian system in such a way. If I'm not paying for it through taxes/etc, it's not fair to those who are.
To me the extra money is just not worth it, though of course everyone has different priorities and so far the states has catered to priorities different than mine.