Personal viewpoint, but I think the cyclical nature of it is difficult. If you always had cramps or felt crazy, it'd be easier to get used to/treat. It's kind of like wondering why adults are bothered by having a hangover, because they've had decades of experience having the occasional hangover.
Adding to that, one's period symptoms evolve as one's body and hormone mixture change. The periods you have as a tween are not going to be the same as you have as an adult, and then you might hit a regular stride but suddenly it's peri-menopause. Birth control that regulates the menstrual cycle is another variable; switching between them or stopping/starting changes the hormonal landscape and its effects on muscle, brain and endometrium. Ditto pregnancy and lactation.
There is a learning curve, though. A 13-year-old is problem-solving a brand new body function for the first time, one that has visible and olfactory tells, surrounded by her feral agemates during the most insecure and self-conscious life phase. A 30-year-old is going to have more knowledge of her body and what helps her feel better, (hopefully) more of an internal sense of self, and is also going to have a stash of menstrual products in her purse/desk.
If you have to pick a cancer, prostate cancer is a pretty good one to pick. The old saying is that people die with prostate cancer, not of prostate cancer. There are outliers but it's really slow-growing, so if it happens when you're old enough, it's just symptomatic treatment.