Yeah, for the same reason that CJK designers often use absolutely abhorrent fonts for English words on packaging and printed media, is the same reason Westerners use terrible fonts for CJK. They are working with a language and culture they have no knowledge of, and think that if the characters look sorta right, then they must be readable and look good.

I've made so many horrible localization errors in the past because I had to translate things into 30 different languages and I can only barely read a handful of them, so I just copy and paste whatever the translators give me.

Incidently, I saw Japanese text recently that was quoting both English AND Arabic in the same sentence. And this was in a block of vertical text. That is literally a worst-case scenario I think. You have RTL-vertical text also containing RTL- and LTR-horizontal text. And unlike English, which when placed into vertical Japanese text, you can essentially choose whether you want the characters going vertically or sideways - you can't do that with Arabic as the letters must be joined together, I don't believe you can break them down and stack them on top of each other.

Why can't we all just convert to Esperanto? ;)