The family and social environment allows boys to move more outward and indulge in many activities. So, they are not so emotional as they get practical. The girls confined at home have less interaction with the people outside home and are passive. This passivity makes them emotional. They can hence express their sentiments in tears only (Dil ke armaan ansuen mein baha gaye).
This does not refer to modern office going girls, who are as practical as boys and so not so emotional.