I really hate Schrader valves. Most of them. Why? Just look at the valves I have in my Schwinn. Try to inflate these tires:
Easy? I don't think so. When you push the pump head on the valve the whole valve dips into the rim and installing the pump on it is a real PITA. Good quality Schraders come with fully threaded body and thumb nuts that secure them on the rim. Like this one:
Schrader valve with threaded stem (Picture from Wikipedia.org)
But these are rare and it is not easy to find a factory built bike that would have them. Most Schraders that come with factory bikes are crap. It is a perfect example how saving a few cents in manufacturing costs does not make sense. The result is a worse product that becomes a source of aggravation for its users.