There is actually a blitzball player in Guadosalam who calls Tidus by name or whatever name you have put in. That's the only instance I know of.
For the voice acting it would have been a massive job to do all sentences with his name twice. Don't underestimate how many tries it takes to get a good take, let alone match the sequence of visuals behind it as it would be different timing with name as opposed to no name.