Obviously, if one person is really 100% remote, there is no direct infection risk. But this might not apply to most employees, there are probably a lot, which mostly work from home and still meet coworkers or customers from time to time. I can very much understand a company not wanting to differentiate in their mandate on a per person basis. Especially as this also would raise the question of enabling 100% home office for all employees and so on.

Also, with omicron, the point of vaccines becomes less about transmission, but also about personal health. Not sure why home workers should be treated differently here than the colleagues.

Disclaimer: I am from Germany, it would be impossible here for a company to require vaccinations. But if it were, I could understand that they would require vaccination from all employees.