About not wanting kids, there are many conscious factors as to why one might not want kids: 
- Financial Considerations
- Career Ambitions
- Environmental Concerns
- Relationship Dynamics
- Personal Freedom (especially in places with war)
- Health or Genetic Concerns

Each person’s reasons for choosing not to have children are unique and valid, but it’s also worth considering the subconscious instincts and biological factors that influence attraction. Evolutionary biology suggests that humans are naturally drawn to certain physical traits that signal reproductive fitness, even if we’re not consciously aware of it.

Human attraction has been shown over time to be  influenced by a combination of conscious and subconscious factors. One such factor is scent, as humans we possess a sophisticated olfactory system that can detect subtle chemical signals (pheromones). As far as I know, the exact role of pheromones in human attraction is still debated, but there are some studies suggesting that individuals may be subconsciously drawn to the scent of someone whose genetic makeup complements their own, potentially indicating genetic compatibility. So even if you don’t want kids, this is still something that’s playing a role. 

And to the butt comment I made, physical appearance still plays a significant role in attraction (like you said some like plum, some like firm… everyone like something different - but there is likely a subconscious reason). Evolutionary psychology point out that certain physical traits may signal reproductive fitness and health (even if you don’t want babies, it’s subconsciously happening), leading one to be instinctively drawn to partners who possess these traits. For example, a shorter girl might show preference to taller men and it may be rooted in evolutionary instincts, as height can be associated with strength, health, and genetic fitness.

Obviously as evolved humans, attraction is highly subjective for us and can be influenced by cultural norms, personal experiences, as well as individual preferences. So while evolutionary instincts may play a role in attraction, they obviously do not dictate or determine our romantic or sexual preferences entirely.