I’m a French dude living in Japan. For a long time I’ve lived with 3 PSN accounts: one in France, one in the US, and one in Japan (also, recently, one in Brazil but that’s another story).
Having several PSN accounts is, in general, not convenient. I have bought games on all three accounts, and it’s a pain to switch. The PS3 and PS4 make it relatively easy with their profile system, but on the Vita it’s a nightmare to use different accounts.
I recently decided I had to choose one account and stick to it. I asked several friends online and in real life for their opinion, and it became clear to me that besides the obvious “I chose the PSN of my country because that was the default option”, people don’t put that much thought into their choice.