Why Translate YouTube Videos into New Languages?
The benefits should be obvious. You get to increase your audience, by having people from all around the world watching your content. This allows for your audience to grow exponentially, which would otherwise only be possible through severe marketing investment. It helps customers to understand your product, services, and or views. Not to mention, you also get to toy with international SEO strategies. This gives you the chance to market products in countries where the keywords you use are trending. They might be trending one day in England, the next week in Italy and then next month, in Singapore.
And of course, you also help those who are deaf or hard of hearing to follow along wit your videos too. People with good hearing might want to turn the volume down and just put your video on in the background, catching glimpses of the subtitles to follow along.