Sleep apnea has close correlation with obesity. Because the sufferer literally stops breathing in their sleep, there is a real chance that their breathing simply fails to restart. The machine which ameliorates the symptoms is portable, but some of my friends who use them resent the machine, and passively resist using it, i.e. do not attach it at night. Also, as for surgery, some people tell themselves that they'll lose weight rather than do the surgery, and then don't do either.