Sexual immorality implies behaviour contrary to the accepted moral code, which may differ according to the society and the group of people concerned. Sexual immorality may therefore include any sexual deviation as well as 'deviant' marriage patterns and violence. It also includes prostitution.
Sexual promiscuity may lead to children borne of two unmarried persons who are unable or unwilling to take care of them. That means that the community may be burdened with their care and may result in psychological traumas for the children, which could lead to deviant behaviour, thus further burdening the community. It also leads to (or is the result of) a diminished feeling of self-worth; and is said to be the main cause of the present dramatic increase in sexually-transmitted diseases.
Society at large has failed to define and support standards of sexual behaviour giving rise to varied and limited sexual codes. The viability and social benefit of any lasting images of sexuality have become impossible to determine. In any case, the biological and social needs of the whole of humanity is rarely, if ever, considered.
If sexual promiscuity were accepted (that is, legalized) it would cause the breakdown of the institution of marriage, which is necessary to the social good, to be less desirable, and it would lead to disorder and strife.