Probably because of a multitude of reasons, but i think it's up to him to disclose why. It's his mod, so ultimately it is his decision that counts.
the mod is subpar and not even remotely close to release. i have abandoned modding beam by myself i just help my friends with their mods now as i find much more enjoyment, i am planning to mod other racing games in the future and maybe a comeback to beam but you can stay sure this mod is not releasing as is it would need a complete remake not just a refresh so yea that is why it's cancelled so now everyone reading this do not reply further i do not want this thread to be bumped again every once in a while