An article in the June 2009 of Contraception calls for a reexamination of withdrawal as a birth control method:

Yet there is a general reluctance among health care providers and individuals alike to consider withdrawal as a viable method of contraception—even as a backup to more effective methods or as an alternative to not using contraceptives at all—which likely stems from misconceptions about its effectiveness at preventing unintended pregnancy. The article examines why this lack of enthusiasm persists despite the method’s relative effectiveness, as well as the consequences of the method’s lack of popularity.

The best available estimates indicate that with “perfect use,” 4% of couples relying on withdrawal will become pregnant within a year, compared with 2% of couples relying on the male condom. More realistic estimates suggest that with “typical use,” 18% of couples relying on withdrawal will become pregnant within a year, compared with 17% of those using the male condom. In other words, with either method, more than eight in 10 avoid pregnancy.

Why not recommend withdrawal? Withdrawal provides no protection against STIs, for starters, and I'm not sure it's a good idea to promote a birth control method that encourages people to believe that they don't really need... an actual method of birth control. Withdrawal isn't birth control, it's orgasm control. But it's hard to argue with this:

[Withdrawal] can substantially reduce the risk of pregnancy for those who have difficulties using other contraceptive methods, including women who have trouble taking pills regularly and couples who prefer not to use condoms, and for those who have unplanned sex and have no other method available to them in the moment. In addition, it is free and requires no planning.