Divine Divinity wasn't fully voiced (and there was a lot less dialogue in general), and the publishers for other localisations handled the voice acting.
Of course it is possible to voice other languages, but the pipeline for doing the motion capture, animations and processing is currently being developed and updated, and there is a delay before text is finalised and then gets translated. Whatever the cost benefit analysis is of other languages, adding any at the same time would be an additional level of complexity to the project.
From this interview
[b"]Jumping back to dialogue, one of the things I don’t like in some RPGs is characters that don’t talk. They speak in Baldur’s Gate III but I noticed they don’t voice their dialogue choices. Was this done as a way to give the character a personality while also retaining many dialogue choices?[/b]
With Original Sin 1, we introduced a tag system. If you’re playing a fighter, you’ll have dialogue options specific to a fighter. In Original Sin II, we kept on adding more and more tags. You made a choice and it has ripple effects. Here, we’re using these things more and more. There are many dialogue choices that are custom-built for origin characters.
This comes down to budget and manpower
. If you don’t have enough writers to come up with all of that stuff, you can’t do it. Without the money to voice record all of it, you can’t do it. If you don’t have the scripters to script all of those different things you can’t do it. We identified the strengths of Original Sin, improved on them, and made them even stronger in Baldur’s Gate III."
If MONEY is the problem you can do a kickstarter for different languages. Yes, it will make a delay but beside the languages which will improve the game feeling much more on the other hand it´s more time for fine tuning and finding bugs. It´s a win-win situation. To reason for a rush release at all.