A have already understood what is the point, when we wrap up in a such a way, this attribute is strongly recommended for being used but not obliged because of accessibility reason
In the great article HTML Inputs and Labels: A Love Story Amber Wilson even generally recommends explicit labels (not nested) over implicit labels (nested):
Unfortunately, an implicit label is not handled correctly by all assistive technologies, even if for and id attributes are used. Therefore, it is always the best idea touse an explicit label instead of an implicit label.