In an organization where people are accustomed to indexing their activities to other people who live in a different time zone, it’s actually easier to use the most common time zones than it is to switch everyone to UTC. When using UTC, you have to do the mental gymnastics twice. You first have to relate your own time zone to UTC, and second relate your audience time zone to it. But what happens in practice is that you quickly learn what times in your local time zone correspond to movements of the day in your peer time zones. And because everybody has the same mental model, it’s easier (and less error prone) to just to use local time zones.