SCCM Solution Template - Why the ETL Model?

I've been using the PowerBI Solutions Template for SCCM for months now. It's great. I've learned to extend the solution to start pulling in more custom data (which was a chor as a SQL/PowerBI beginner without a lot of documentation out there).

I'm curious on why the Solutions Template is setup as an ETL model - by pulling in certain pieces of data to a separate DB and then querying that DB?

Why not just query the SCCM DB directly?