In case of short controller that don't use qweb template, we don't need anyhting else that this url code that don't change frequently. It make only sense for model like lang, website, ... that will not change frequently. And are called on each call by the dispatcher. In case of a website page, we will btw browse lang later, but in case of small controller like /favicon.ico, or page without qweb, ... we can just use the same from last query.