The sounds need to be redone from scratch, in a studio. Many mods may use sources from the internet, that aren’t able to be used in a commercial project (source). DayZ is not designed well for client side activity (generating sounds just for you) – it’s been designed from the ground up to generate information from the server and send to the client.

They would have to record and synchronize all the information, for both sexes. Probably with the different voices for variety. The dev team would then be beholden to that voice actor for everything, adding about three or four weeks to any new feature to capture the audio. That also takes up at least one audio channel and will require a dedicated thread to figure out what sounds to play and when.

Also, they then have to localize it in every language (10+ languages). This is a huge amount of work. That means they have to record 20-40 tracks for each effect it is applied to (source). In the pre-alpha, the gun sights are not displaying the highest LOD because they are proxies. It was a bug discovered before filming but I decided to film anyway. There are hundreds of bugs just like this.

Sounds will not even be considered until they pass the alpha milestone review. There is no point adding sounds until you confirm all the sounds you need (i.e. more-or-less feature complete) (source).