The mandate is weak enough that there are still healthy individuals who aren't covered by company plans who are choosing not to buy insurance. [ADDED: And there's a fair bit of concern that the number of these individuals will rise as rates go up, driving further rate increases, in what's often called a "death spiral.]
There are non-employer group plans for certain types of insurance e.g. through something like the IEEE but generally not for healthcare AFAIK.
With respect to disability--leaving aside that an exam won't find all pre-existing conditions such as joint problems--there's still adverse selection. The people who would even apply for disability insurance are a higher risk pool (probably older for one thing) than the working population as a whole or all employees working at a large company.
There are non-employer group plans for certain types of insurance e.g. through something like the IEEE but generally not for healthcare AFAIK.
With respect to disability--leaving aside that an exam won't find all pre-existing conditions such as joint problems--there's still adverse selection. The people who would even apply for disability insurance are a higher risk pool (probably older for one thing) than the working population as a whole or all employees working at a large company.