It isn’t really for people working in actual instruction. It is more about policy and methods. I had a friend get a PhD in Educational Psychology. His research area is computer aided learning. He has a BS/MS in CS. Many of the people in high ranked PhD Education programs are looking to go into academia (university level), consulting/think tanks, or government.
If you want to read what some of the PhD alumni do, it is here. Learning Sciences Alumni - Educational Psychology