If you are a male you should be aware that the ONLY thing that makes hair grow is ANDROGENS. No matter how much hair you remove the androgens will still be there unless you have them removed by a surgeon. As for females.... the ovaries make testosterone and that is converted to estrogen. If you make more androgren than is converted to estrogen you will still have androgens in your body. Progesterone is also a hormone that makes hair grow on females in places where only males grow hair like the face, back, chest. If you take birth control pills read the label in the package for side effects and you will see that hair growth is a side effect of those pills. Also, the needed adrenal hormones have activity that is the same as androgens or testosterone.
If you have (for example) 100 hairs per square inch they are all not growing at the same time. Whatever lasers do they can only do when hairs are GROWING (WITH PIGMENT IN THEM) and they are not all growing at the same time. The follicles were there but not yet mature enough to produce terminal hair. All the glands are there when you were born but not yet mature enough to produce the hormones that make sexual hair grow (you have hair on your head, lashes and eyebrows but that is not sexual hair) because you do not have all the hormones until puberty.
*keep in mind the medical term for excess hair in places where women usually do not grow hair is HIRSUTISM. This can also be due to an ovarian disorder, adrenal disorder, or a brain disorder that can be treated with medication. Check it out because sometimes it can prevent ovulation and causes infertility.