This negative attitude towards a wonderful aspect of the human body is a major problem. We are doing something wrong. Don't knock masturbation. It's having sex with someone I deeply love. Masturbation and intercourse do not necessarily replace each other.
Men usually ejaculate easily but women frequently have trouble climaxing.
One reason for this is that men masturbate by grasping and stroking the penis with one hand. This is similar to the movements and sensations during intercourse, so for men masturbation is good training for intercourse. If one learns to have a climax in only one way and if that way is incompatible with intercourse, e.g. by squeezing the legs together, it may be difficult to achieve an orgasm when having intercourse with a partner. Women need to research these matters. There is another aspect of masturbation worth noting.