[dfc]

There are lots of cultural and legal forces that deter suicide. (hopefully you were not being pedantic with prevent/deter)

  * Cultural shame of surviving family.
  * Suicide is a sin in some religions.
  * Suicide voids most life insurance policies.

[matteotom]

I think in most cases, suicide only voids life insurance policies for the first 2 years of having the policy. It makes sense, since it prevents people from buying life insurance when they plan to kill themselves.