Yes, BYOP is for more advanced users for sure. Which is probably why they are not selling them at Walmart directly.
It is particularly complex on the iPhone, but on many other devices (Android particularly) it is very, very, easy.
So I wouldn't blame Straight Talk for it, at least to start. They could train their agents better (Tmobile has specific CSR training for people who want to use the iPhone on their network) but prepaid carriers don't have that luxury. ) You get what you pay for, budget prepaid service means budget service.
Go GSM! Switch phones on demand.