Why? It's the original intent and the original voice. The sub tends to be closer to the original script because they aren't constrained by mouths moving nor can they add lines, music etc. I don't think voice acting is as well respected in North America too and so lack of talent/desire to keep costs low gets a worse result. I don't think it helps that English VAs will sometimes try to mimic the Japanese VAs but it just doesn't work and easily sounds really grating. I have turned off voices in several JRPGs because of this.