Fuel shutoff valve
 

I'm posting this question in general as it doesn't apply to any specific brand or bike and apologize if this has been brought up before. I have noticed that many manufacturers install a fuel shut off valve ( usually on or near the tank) and then a fuel filter ( somewhere near the carb change). I'm confused by this as it would make more sense to me to install the filter then the fuel shut off so that draining the carb doesn't have to involve draining the filter and line also. any thoughts?