I agree that if SCOTUS approved the mandate, employers wouldn't have the difficulty of creating their own plan. On a benefit side, it will allow for data to be collected on employee responses to these decisions. Many companies decided to do a wait-and-see approach and may still wait it out for others to take the risk. If a company wants to mandate, they need to be prepared for a loss of employees and customers as has been witnessed in airlines and medical fields. Draconian measures and regulations do not play well with the American public, no matter what side of the aisle.
I'm going to make the assumption that most commenting to these threads are either working remotely or in distanced offices likely in larger cities that already have mandates in place. Outside of those spaces, you might be surprised by much of America not wearing masks and numbers averaging around 50-60% of employees being vaccinated. It is common knowledge that being vaccinated doesn't mean you won't contract COVID or won't spread the virus, so it would appear to be unfair to not provide testing to all employees.