A few releases ago (currently running 2017), Solidworks changed the way that the first inserted part is placed in the assembly. It used to place the first part origin-to-origin automatically. Now, it just allows the user to randomly place the part wherever he/she wants - with no regard to the origin.
I can see pros and cons to each scenario, however, I wish that there was a way for the user to make that choice upon inserting the first part. Or is that an option?
Is there a "switch" somewhere that you can trigger to ask if you want this part placed at the origin?