A 2017 study in the Journal of Sex & Marital Therapy (which included more than 1,000 women) confirmed what sexologists have long known—penetrative sex alone is not enough to achieve orgasm for most women.
Anatomical reason: The clitoris, not the inner walls of the vagina, contains the highest density of nerve endings. During penetration, the clitoris is stimulated indirectly, indirectly — which is not enough for many.
What the study says According to research, about 18% of women achieve orgasm through penetration alone, and most need additional clitoral stimulation — this is statistically the norm, not the exception.
Practical Solution Adding clitoral stimulation with your hand or a toy during penetration (the "screaming" position is especially helpful for this) significantly increases the likelihood of orgasm.
Why this information is important Not knowing this fact can create a false sense of "something is wrong"—in reality, it's simply a matter of anatomy, not a problem to fix.