The plural of haiku is haiku, and if you become steeped in haiku writing, you will know that it's not that easy to write a great one. And contemporary haiku poets know that most published haiku are not written in 5-7-5 format.
haijin
The plural of haiku is haiku.
And if you know anything about haiku poetry, you will agree that writing great haiku is not easy.
Also, the 5-7-5 format is not frequently employed by contemporary haiku poets.