Users cant create private plans

Hi all,

I am trying to understand why users cannot create a private plan at all with MS Planner. As an administrator, I have options below:

However, standard users can see the below. They have - "add to existing group" as required. That means that I have to create a group for a user that want to use it for tracking his project personally/privately and then assign it. 

What is the reason for this? How to deal with it please?

thank you for any advice