I agree with others that I don't think most CEOs are going to give truthful answers in such a study. The way I see it:

For many there's just a preference/productivity boost for working in-person. That's fine, remote is not for everyone. However my hunch is that if decision-making management is mostly comprised of older millenials and gen X, they're just habitually used to working in-person and refuse to change.

Then you can go into the darker reasons:

Ego around owning an office space and then having to use it, "fairness" (read: superiority complex) against workers getting the same perks as managers, inability to work in a remote (read: digital first) culture, easy way to get rid of people without paying layoff severance.