I'm not sure whether this is a bit of trolling, so I'll just take it seriously and thus frame my reply.

Part of what all unions, and for that matter, all workers including management and CEOs, negotiate for nowadays is some sort of retirement benefit. The company benefits by giving an incentive for experienced well-trained personnel to stay on for as long as they can, so that the company is not constantly training new people for positions in the company, and undergoing the loss in efficiency and increase in labor cost due to mistakes made by inexperienced personnel. The worker benefits by not having to worry about the vagaries of the stock and bond markets with respect to his or her retirement money. This becomes more important as the average educational level of the employee decreases, and the physical demands of his or her position increase, and the likelihood of work-related injury (chronic and acute) increases. The company benefits also from the good will and loyalty thus engendered, and also the fact that the worker now has a stake in good outcomes for the company and could presumably be encouraged to work towards those good outcomes.

The other alternative is to have a business with high labor turnover and low employee satisfaction, such as in fast food, service industry (like restaurants) and retail, which tend to be paid at or near the minimum wage. If however the work is dangerous or requires expertise and experience, it's wise to have a contented workforce which will not walk out or quit suddenly. Oil drilling and refining is a good example of the latter.

When a company makes a formal written contract with an employee or the employee's agent, the usual master-servant employment-at-will doctrines do not apply, namely that one receives a day's pay for a day's work, and that one can be fired for a good reason, a bad reason, or for no reason at all. Instead, the law created by the contract now controls the relationship and the outcomes. If the employee contracts with an employer for an old-age insurance policy which will vest in a given finite amount of time and pay out a sum certain over a period of time and such other benefits as may be contracted for, as partial compensation in exchange for the labor of the employee, the company is obligated to provide such insurance and to pay on it, or be liable for its breach.