For one thing, jobs. Secondly, not everything is available in stores. Buying from someone local is keeping a person employed and money in our economy, but it also means if I have a problem it's easier to return. If i am buying off eBay, first thing I do is check for local and then go overseas. At the moment, I now have to do in depth checks of sellers despite their feedback levels because eBay isn't doing anything to change it.
I have no issue with buying from China. I do regularly. I just want to know when I am doing, not when I buying something local I expect to be here in a week and having it take 4.