Women who are nursing their babies, can experience pain in the perineal area (the tissue between the vaginal opening and the rectum). A lubricant or moisturizer in this area can be enormously helpful. It can help improve the elasticity of the tissues and decrease the friction upon penetration and that will make sex more comfortable.
After that certain age:
As we age, sex for many women can become more uncomfortable, if not downright painful. This is due to physical changes that result from menopause. The hormone estrogen decreases and the result is decreased elasticity and lubrication of the vagina. Many of my patients have found that an all-natural lubricant can ease the discomfort and add back the sexual enjoyment.