Because disrespectful chatty Soseki translation is what we do best.

俳諧の趣味ですか、西洋には有りませんな。川柳といふやうなものは西洋の詩の中にもありますが、俳句趣味のものは詩の中にもないし、又それが詩の本質を形作つても居ない。日本獨特と言つていゝでせう。
一體日本と西洋とは家屋の建築裝飾なぞからして違つて居るので、日本では短冊のやうな小さなものを掛けて置いても一の裝飾になるが、西洋のやうな大きな構造ではあんな小ぽけなものを置いても一向目に立たない。
俳句に進歩はないでせう、唯變化するだけでせう。イクラ複雜にしたつて勸工場のやうにゴタ／＼並べたてたつて仕樣がない。日本の衣服が簡便である如く、日本の家屋が簡便である如く、俳句も亦簡便なものである。
A feeling for haikai? Not in the West, nah. They have things like senryuu in their poetry, but nothing like haiku, which aren't even really "poems" anyway. You could probably go ahead and call those suckers unique to Japan.
I mean, think about it. Japan and the West are different even down to the way they build and decorate their houses. In Japan, something as small as a tanzaku can really pull the room together, but the West builds on such a large scale that you wouldn't even notice such a teensy little thing.
Haiku aren't going to evolve, just change. You can make them as complicated as you want, or throw a bunch together like some crazy bazaar, but it won't mean squat. Japanese clothes are simple, Japanese houses are simple, and in the same way haiku are simple too.

Ha! We sure showed him.