The game is designed for players to read the text. In this case, there's nothing complicated. The mechanics are fairly straightforward, and there's a built-in help system for any confusing situations.
The number of languages generally depends on the activity and desires of individual community members. For example, Chinese (simplified script) is expected to appear in the stable version 0.73 because one person wanted to teach the game their native language. Polish may appear in version 0.74 (based partially on human and machine translation).
The game's creator can't teach the game to all languages themselves; there's too much text, but they add translations created by the community.