Because it's a format rarely used outside of an engineering context. If your users are 100% from a technical background, and always will be, fine. Otherwise, a lot of your users will find it difficult to parse dates in this format.
back
2 comments
According to the map of date formats in the article, there are a lot of people worldwide who use this format outside of an engineering context.
In my country (it's small, I admit that) yyyy-mm-dd is official date standard.