Why can't plain Android be configured with an Exchange account via MDM solutions?

[AC Question]

AFAIK you need to use one of the following:

- a container solution (not stock Android, additional costs)
- Android for Work (free but sucks before Android 7 because contacts are not available in the dialer)
- Android Knox (not stock Android)
- or something else.

Does anyone know why Google decided not to make EAS provisioning possible on stock Android?