It’s just a fun thing to do….it’s all tongue in cheek.
I’ve had a Peggy, a Priscilla (which became Psycho) and currently have Rocky. I suppose for us, it’s easier than saying “No, not that Peugeot, THAT one”
Back when I was changing manufacturer and model pretty much every time, it was less needed, although we still have some issues over Astras, so we have original Astra and Ebay Astra to differentiate between the two.