Understanding Devops with PBI

hey team, 

a quick question:

I published a PBIX onto a workspace and this workspace is git integrated. 

i commit the changes from the workspace and i see the 2 artifacts in my Devops repo. 

I thought i had to create a PBI project .pbip to enable git publishing. that is not clearly not the case.  

So why do we need .pbip? 

Please can someone shed some light on this .

thanks