They don't want to be and they're not really acting like it. Thus their store's quality is similar to or below that of ebay and far below that of directly chinese stores like Banggood or Ali Express.
I've been using Alibaba/Ali Express more often lately, and am finding that they are improving rapidly. For most products manufactured in Asia, they're significantly cheaper.
Quality is more consistent. It's not that everything there is better quality, but that you can more easily determine the level of quality you're willing to pay for and can be relatively confident what you're going to get.
Shipping time and (perceived) shipping cost are the big things that prevent Ali from growing rapidly in the US market. They're a few warehouses away from being a serious competitor to Amazon's retail business.
That's a very good point. I don't see how they expect their costumers to believe in quality of their own products with this attitude.