Remember, we have to sell to people all over the world and one country's standard "default" may not match what the rest of the world does. 🙂
I think we cover setting number of p/py as the very first item when we hit the finance section in the manual you get. Also, know that "clearing" the settings doesn't touch the ppyr setting at all. Now that you've set it, the only time you'd have to ever set it again is when the battery goes completely dead for long enough the full memory get wiped.
Although I work for the HP calculator group as a head developer of the HP Prime, the views and opinions I post here are my own.