Why is it "suspicious" when you're already logged in on PSN?
I also find this to be very annoying - and bafflingly enough it happens even if you've already authenticated yourself to PSN.
If PSN login is good enough for every other game on the PS3/PS4, why isn't it good enough for FFXIV?
I haven't played FFXIV on Steam, but the same idea should work there: if you're already logged into Steam, it really should not reset your password just because your location or IP address changed, and you really shouldn't have to enter an additional password for FFXIV every time you play.