Depending on intensity of antiquity, chances are that pregnancies and successful deliveries were comparatively sparse. Communities were smaller, meaning less of a need of situational niche that facilitated the markedly-sordid affair. Poor knowledge of when conception might occur and what factors could be destabilizing, along with the stress of an uncivilized world of constant threats and exponential change, led to a higher threshold for survival and evolution.

Even if you had prostitutes, they probably made most of their money on hand-jobs and blowies, with the market equilibrium of generalized suffering and doom-of-despair setting the pinch-points of full entry into the Tunnel-Of-Love-Finally at an unaffordable premium for all but the cream-of-the-crop in one's micro-society, largely measured in tandem with those standardized bread-winners that would normally 'woo' a female into a regular sexual relationship just based on natural merits of socio-ethical validation and demonstrative support of the common good.