That's really more due to the influence of the King James Version than anything else. For example, ESV uses you: https://www.biblegateway.com/passage/?search=Matthew%206%3A5...

In French, however, God is always referred to with the informal tu, which surprises second language learners. But it makes sense when you realize that using plural for formal came about well after the Hebrew Bible, and because it was to implicitly refer to multiple people (sort of like the royal We), which obviously wouldn't be acceptable in Christianity.