The answer to this question lies in the biological and social roles of males and females and in the way that sex toys may replace the role of men in those relationships.
Simplifying the subject considerably, evolution has resulted in most species having males and females for sexual reproduction resulting in the sharing and diversification of the gentic pool. However the existence of two ‘versions’ of a species has also allowed the development of specialisations/roles for the males and females.
In mammals the main biological difference is that the male provides sperm and the female provides eggs. After fertilisation the female has the role of looking after the embryo in the uterus (womb) and providing milk to the offspring after birth.
With this simple view the male provides only the sperm and a widening of the gene pool. However it would generally be too expensive in resources (in evolutionary terms) for that to be the only role of males, and so social responsibilities have evolved. Males often look after their mate and offspring by helping to provide food, protection and a ‘home’.
With humans, changes in much of the world...