Because you either manage people / goals / interactions with other teams or do front line work. If you cross the barrier the people in your team will be put un

Because you either manage people / goals / interactions with other teams or do front line work. If you cross the barrier the people in your team will be put under pressure having to do things like for example disagreeing with technical decision or debating something in a code review with... the same person that has the power to promote or fire them. It creates a power gradient in every day activities. That's "stealth" micromanagement regardless of the good intentions and technical skills of the manager.