We don't have rules for battleship.

I guess its because battleship is such a popular game, most people know how it works and don’t need battleship rules?

Well yeah, the game is popular, but at least, we should have a short description or a small highlight on the mecanics they adopted here, cause on every platform, it is a bit different.
On the other side, I can understand why we wouldn't need rules that badly, as it has been previously mentioned.
Views can be different, but I assume this might not be such a priority.

I knew battleship here but not elsewhere.

There are a lot of variants, both on online platforms like this one and offline for download