Officially it is to prevent kids from getting corrupted from video games. They are only allowed to get corrupted by violent games on their phones and PCs. 

But you could wonder if it has anything to do with the fact that Sony and Nintendo are Japanese and Microsoft is American. 

Still, games are openly for sale, it even looks as if it is possible to buy games that are NOT pirated. 

Yeah, you know prostitution is "banned" too but you can find it just as easily as game consoles.  It's one of those stupid laws that's never enforced.  It's already in it's 12th year now and there are rumours it's going to be canceled.  

God knows why they ever came up with this law.  Possibly because the government thought China would be able to come up with their own game console and wanted to protect Chinese products.  Who knows.