The F&PB / Parliament acts on behave of pressure groups. (?) BUT The prudes and religious hypocrites are not the only ones who have a say. Club owners / publishers / webmasters / concerned public members can also form a lobby and demand that their interests are respected in parliament.
Contrary to what the prudes and religious hypocrites want you to believe; sex and glamour is not sin!
South Africa is a democracy with a constitution. The Film and Publication board / Parliament can't just make laws as THEY want.
Outdated / impractical laws can be revoked, e.g.
There used to be a law that alcohol may not be served in strip clubs. Teazers continued to do so until Lollie was arrested. After his case has been heard, the law was revoked. (In retrospect, I suspect Lollie engineered the whole case. Viva - Lollie, the man!)
Recently the abortion law has been revoked, because it was felt that not enough input from the public has been solicited before the law has been passed.