Also, I forgot to mention. It is difficult to forego health insurance coverage because in most states, this can mean never having private insurance again. Suppose I'm healthy and decide to work at a startup that doesn't offer health insurance. I figure I'll pay for doctor visits out of pocket. But while I'm working there, I discover I have cancer -- I need lots of treatment and there's no way I can pay for that out of pocket. But I can't get private insurance now because I have a pre-existing condition. Insurers can (and will) simply refuse to sell me a policy. If my condition is manageable enough that I can switch to a regular job that has employer provided insurance, I'll be fine because employers generally arrange with insurers to not have any pre-existing condition limitations, but if I'm too sick to get a good job with insurance, then...

Well, you can see how this can spiral out of control until I end up blowing all my savings on health care bills and eventually have to declare bankruptcy. That's the kind of fear that keeps people in boring corporate jobs: the gnawing uncertainty that even if you're healthy now, you (and your family members) are one major medical crisis away from financial ruin and being forever locked out of the good insurance system.

Now, this doesn't apply in MA today and as the new health care law goes into effect over the next few years, it won't apply anywhere in the US. Sorry to write so much, but in my experience, people in the UK just have no reference for how screwed up American health care is and how much fear it can inspire.

For odd historical reasons, when an employer purchases health insurance for an employee, they get a huge tax deduction. So having employees buy their own is significantly more expensive, even for the exact same coverage. In addition, in most states in the US, the individual insurance market is a disaster: prices are outrageous, there is no common market where you can look up prices so you have to find and contact individual carriers, you can be denied coverage for just about anything, coverage standards are non-existent so there's no way to compare plans based on price, etc.

The end result is that many developers aren't willing to take jobs where health insurance isn't included.

You'd have to pay a hefty premium to get an experienced developer to take a no-health-care gig. I'm in an employment transition right now and my COBRA (transitional health care plan offering provided by law) costs add up to about 11% of my gross salary. This isn't even the top-tier plan.

Right now, it depends on state law --- required in at least Massachusetts and Hawaii, but many other states have no such requirement.