Untouched Name Explained

In my earlier post this month, I wrote about westernized character names in Case Closed, the English version of 名探偵コナン (Mei-Tantei Konan), or Great Detective Conan. During its translation process, names of protagonists and some recurring characters were renamed into ones familiar to western readers. Below is a list of westernized names and their original counterparts which I've so far found as of the second volume.

Jimmy Kudo (the main protagonist) ⇦ Shinichi Kudo 

Rachel Moore ⇦ Ran Mohri 

Richard Moore ⇦ Kogoro Mohri 

Amy ⇦ Ayumi 

George ⇦ Genta 

Mitch ⇦ Mitsuhiko 

Now the question is, why the hell didn't the translator touch the Shinichi's surname? 

Well, you can find the reason behind that in the second volume. Jimmy's classmates at elementary school invite him to explore an abandoned creepy mansion which is rumoured to be filled with strange books. The kids claim that its owner "Eto" was eaten by a demon. A little later, this mansion turns out to be Jimmy's. There is a nameplate at the entrance of the premises, which reads 工藤 (Kudo). The truth is the classmates confused the first kanji for a katakana character "エ" (e). If the surname were an English name, this plot wouldn't work. Kudos to the translator for preserving that! 

But now the second question arises. Why in the name of fuck did they change those names to begin with? Shouldn't they have left the names unchanged? That would have been a whole lot easier!