So any reason why they changed his character's name? I understand the Paris/Locarno thing because they were different enough (sort of) but Vorik was a very secondary character, I don't see any reason to change him.
It's all because of royalties. The character of Tom Paris exists because if they had used Locarno, the writer of "The First Duty" would be entitled to get paid every time the character was mentioned.
So it is with Vorik. That character only exists because otherwise whoever wrote the first TNG episode with Taurik would need to get paid.