Why do some insurance companies cover Viagra but mine does not cover prescription contraceptives?

It's not fair that some health insurance companies are covering Viagra but my company doesn't cover prescription contraceptives.

It's true that many health insurers started covering Viagra after men began scrambling for this impotency "wonder drug" and yet they don't cover contraceptives. But there's been a movement afoot to make it an equal playing field.

There are 24 states that have enacted laws requiring group health insurance companies to cover prescription contraceptives if they cover other prescription drugs and devices, and other states have similar proposals pending, according to the National Women's Law Center in Washington, D.C. The National Conference of State Legislatures reported in 2009 that mandates in two states, Texas and Virginia, require that employers be offered the option to include coverage of contraceptives within their group health plans. Some laws prohibit insurance group plans from excluding contraceptive services and supplies. Other states also recognize an exemption for employers that object to contraceptive coverage for religious reasons. And several states require employers to notify employees of their refusal to provide contraceptive coverage.

Arizona, Arkansas, California, Connecticut, Delaware, Hawaii, Illinois, Maine, Maryland, Massachusetts, Michigan, Missouri, Nevada, New Jersey, New Mexico, New York, North Carolina, Oregon, Rhode Island, Texas and West Virginia have mandate exemptions based primarily on "religious reasons" for insurers and employers. Opponents of these laws say they will drive up the cost of health insurance. Advocates contend that the estimated cost of $30 per month for birth control is much cheaper than the cost of unplanned pregnancies.