We should worry about loosing lust as the guiding principle for the reproduction of our species.
Throughout history human beings have executed great wisdom in choosing partners for reproduction through the guidance of instincts and intense desire. Much of the aesthetic pleasure and joy we take from watching other members of our species is rooted in indicators for fertility, gene quality and immune system compatibility. Thus our lust holds considerable prudence.
When it comes to the number of offspring, we have now collectively managed to stabilize the world population by the middle of this century through decentralized decision-making. The demographic transition is not a result of scientific planning but of the biological cleverness of individual couples.
The stabilization of the population means that it is ever more important that the biological preferences expressed in lust dominate the reproduction since fewer babies are born and they will live longer.
Attempts to rationalize reproduction through biotechnologies and screening of eggs, sperm, partners and embryos will interfere with the lust-dominated process. It is worrying that this could mean the loss of an evolved expertise in survivability.
Also, the desire to reproduce leads to the advertising of good genes and general fertility through a cultural and societal display of skills and sexiness. These are major, if not dominant sources of the unconscious drive for creating great results in science, art and social life. Attempts to shortcut mating preferences and the matching process through clinical control could lead not only to a loss of quality in the offspring but also to a loss of cultural fertility.