It is more formal to call people by their first names, so the distance between people is far away, and people who are unfamiliar will call them by their first names. When you are familiar with it, you can add a small word in front of your name to make it look close, and it is also suitable for the same level or superior to address subordinates.
For those who are getting older, they are generally getting older, which also means getting close.
Of course, for leaders, it is still necessary to honestly add names such as Manager Li and Manager Zhang, which are generally preferred by leaders.