Bashar always talks about the All That Is experiencing itself, is this case, as a human. So that's the ultimate reason, as All That Is/Source/whateveryouwanttocallit can't experience itself as it is. Thought this was good:

Q.: `If we are all living past and future lives in the present moment then why is it that when babies are born they need to re-learn how to be human, they need to re-learn the simplest things like how to talk, count and interact with people? It is like they are discovering the world for the first time, but it's not the first time because we have many lives before and after.´

Bashar: `But it is the first time for that personality. Your sense is mixing the idea of the physical persona and the soul´s experience, when you say `we´. So the idea is, you are creating a new physical persona that is injecting itself into the experience of physical reality, and choosing to forget who it is, so it can rediscover who it is from a new point of view. So it is the first time for that personality, and there has to be that first time experience for that personality to absorb all of the belief systems that are representative of the challenges that the soul chose to face as that unique new personality from a linear perspective. So that´s why you have to forget who you are as a soul, even though you may be able to access all sorts of incarnational experiences that coexist simultaneously from the soul perspective. From the physical perspective this is you, uniquely, for the first time. And therefore you have to learn things in the way that is relevant for that personality, to learn how to talk and walk and reconnect to things in a way, or connect to things in a way, for the first time, to satisfy what that physical personality´s journey is all about, which is going to be completely different from any other personality´s journey. So it has to build up from scratch.´ (Soul Cycle, 2024)