Simply put, yes a business should always at least contribute, if not pay entirely for an employees health insurance. Realistically an employee is going to spend most of their time working rather than being on their own time, so any health complications they do get are most likely work related, whether that be a flu thats going around the office, or being directly injured as a result of the job (for example a construction worker falling from a roof). This is why employers have a responsibility to ensure their workers are healthy and have their health costs met, particularly if they cannot work because of becoming ill because of work, otherwise leaving them doubly out of pocket.
Many workers will also be willing to accept lower rates of pay for a full medical plan, and as large companies can get better rates than individuals, a company can actually save money by offering slightly lower pay scales, with medical benefits, than by paying their employees enough to comfortably take out health care policies privately.
Knowing they are being looked after by the company will of course make workers feel more valued and more secure in their jobs, which in turn will encourage them to stay in their jobs longer, decreasing staff turnover, and also encouraging them to be more loyal to the company, meaning they will also work harder and more efficiently, increasing profitability and shortening production times.