Because it would cost an extra 5 yuen on a bike that will probably be stolen within a week.

most people think whether have those litte devices or not is not a big deal. so our factory just cut them off.

Because that would imply that someone else exists in their little world that they might need to look out for...

Indeed...a strange phenomenon! If they just had more reflectors, I'm sure the number of accidents would go down, especially since you can't see cyclists in the dark. I would say the government has a responsibility but they are too caught up with other things to deal with this. In many Western countries, you would be fined if you cycled at night without lights or reflectors. And it's not just a law written on a piece of paper, it's actually enforced. China needs to start doing the same..hell, they've got enough manpower to start enforcing stricter rules regarding safey (and even smoking) but again, their interests lie elsewhere at the moment...

Reflectors are only put on bikes when they are required by the goverment regulations of the countries they are being built for.
I can guarantee that China does not have these regulations, so why would a bike maker waste 50 cents putting them on a bike?

Because The local govt considers them cheaper than putting in "speed bumps"!