I'm trained to administer them, and have done so. If they hurt, the nurse fucked up and didn't do it right. It is grossly mischaracterising of a process you have never taken part in or administered to say that it hurting is normal.
Now it may be indicative of shitty nurses, but that's not really an issue with the test itself. If your breasts hirt ftom mild compression, rather than merely feel uncomfortable, you have an issue with your breasts. It should only be mildly more uncomfortable than a self examination.
As for not needing one. Risk of IDC - the most common form of breast cancer in women - starts rising at 25. Drastically increasing at 30. You should really be doing self examinations for lumps and a mammogram every 2-3 years. Post menopausal is the most dangerous time, but it's a disease that can and frequently does emerge in younger women. Same for men and testicular cancer. Self checks are boring,but can be life saving. You wouldn't let yourself get sunburnt all the time would you?