From a purely business perspective a COVID-19 infection is highly disruptive to business operations. If you're following CDC guidelines (and some businesses legally must) then a COVID-19 infection causes you to not only lose the infected employee for the duration of their illness, but you lose every other non-vaccinated employee who has had contact with that employee for two weeks. I know of at least five businesses near me that had to close down for two weeks in the fall/winter due to COVID-19 infection - they didn't have enough non-sick, non-quarantined employees to operate.

That's why an employer might mandate vaccinations for their employees.