I believe that historically crying was seen a weakness mainly, as from survival point of view this was not a quality that helped to survive or address the incoming danger. However, in some cultures, crying has been (and still is) seen as a necessary part of their culture and society.
For example in some indigenous tribes when something happens or somebody dies, crying is used as catharsis to let go of emotional tension, stress and grief. Which is emotionally a very healthy choice.
In today's world, majority of people would probably still consider crying as a weakness, however, in the fields and circles where people have a better understanding of emotional health than the average person in our society, ability to cry would be seen as a strength as it shows that the person has a healthy way to let go of emotional tension and stress.
In the future, once our society develops to understand emotions more and the function and usefulness of our emotional mechanisms (such as crying), crying will not be considered a weakness, but a sign of health.
Allow yourself to cry, it doesn't make you weak, it releases it.