SSAS Tabular Queries Disregard Model’s Relationships Unless a Measure is Included (Except in Power BI !)… Why?

Here is an example that drives me nuts. I have an SSAS tabular model consisting of a parent/child relationship between 2 tables:
Table 1) REGION (logical parent of Area)
Table 2) AREA (logical child of Region)

The REGION table contains