During World War II the US Government controlled prices and pressured unions not to strike. The war ended and price controls were still in effect for a few years. Since employers could not increase wages, they offered increased non-wage compensation such as health insurance. The IRS agreed that employer sponsored health insurance is not taxable income. Thus tying affordable health benefits to your job. (And giving employer health plans a big tax advantage over buying it yourself).

No it's because there was wage control during WWII. Employers started offering it as a benefit to get around the caps.