[metric10]

It's a hold over from World War 2 wage controls. Offering to pay health insurance on the side got around them. It no doubt continues because of the pre-tax benefits. That is, if your employer pays for it then it isn't subject to federal and state income taxes as well as FICA taxes. Depending on your income level and state, those could be around as 30-35% at a programmer's salary range.

[walshemj]

I know someone who while working for Citbank was paying around 25% that just for his insurance (for him self his partners some FBI officer) - makes the UK's NI at 13.8% seem very good value.