Why Can't Meta Predefine Audience Segments for Us?

Why can't Meta predefine the Engaged Audience and Existing Customers audience segments for us? They have the data to do this. Advertisers can't utilize Audience Segments -- and see the power they provide -- until these segments are defined. Many advertisers are confused, or completely oblivious, about how to define them -- and why they should. By predefining these audience segments, it eliminates a step. Advertisers should still be able to edit and augment the lists, but this could be a helpful start.