Does making abortion illegal end the practice of abortion? No.
Does making abortion illegal significantly reduce the number of abortions? Yes.
Does making abortion illegal increase the number of orphaned and unwanted kids? Yes
But you are also correct, the 2 larger issues are preventing unwanted pregnancies, and creating realistic alternatives to abortions.
Both are tough and hard to solve, so we just focus on the legal/illegal issue instead. It's much easier to pick a side and draw a line in the sand. It would require time, effort, hard work, and actually giving a **** to figure out solutions to the real issues. American Idol commercial breaks aren't long enough to deal with those issues.
On a more lighthearted note, I propose a new government program. Hookers for High Schoolers. Supply every HS with an adequate amount of hookers that have been fixed and are regularly tested for STD's, so there's no need to worry about pregnancy. Everyone wins:
1) Guys get laid
2) Far fewer unwanted pregnancies
3) Reduction in STD's
4) Jobs created
5) If you make everyone have a 1st hour class of banging a hooker, I guarantee an improvment in attendance, grades, and grauation rates.