This has been somewhat mitigated by giving us dialogue options. Sure, they are entirely superficial but they do let us give a little character to the WoL. My personal headcanon for my main is she's very sarcastic. The added options are a nice touch. Voice acting, on the other hand, may throw off said headcanon, especially given they will have to write our character a specific way. Putting that aside, the sheer logistics for a voice acted player character in a MMO would be insane. We're talking several millions of dollars allocated to a relatively small aspect—more if our character suddenly had additionally dialogue included. It just isn't realistic.
Even if it were feasible. I would be quite annoyed to see all that money going towards our player character speaking a few times in the MSQ in lieu of more actual content. Let's face it. The cost has to come from somewhere.