Why the lecture at the end?

Why did the screenwriters see the need to indulge in a silly "fate" lecture at the end of this movie? Everything else about it was great. Then right at the end they have to spoil it. I couldn't believe Ewan McGregor was spewing out this stream of glurge with a smile on his face.

The whole movie just happens. Sure, it's "engineered" by a couple of people from another life but that's okay. It all works. But why bother to create a couple of interesting, slightly off-centre characters, put them through a life changing experience and then rip all of that out like that?