system
A chat on subreddit /r/NoStupidQuestions
human
I think general health is worse too which affects fertility. Obesity is high and can cause issues conceiving. My friend tried iui a few times before option for ivf. She was told the both needed to lose weight to be eligible for it on the nhs. They lost the weight and conceived before even having ivf after years of trying. 

But there are still many people not struggling with infertility. Many accidental pregnancies, pregnancies while in birth control etc. I’m one of 4 siblings and we all have multiple children with no issues at all conceiving or carrying.
gpt
Great observation! Yes, I bet that is one of the bigger factors like you said. Obesity or even just not moving each day or mindful eating—all can lead to issues that look not connected but are. Not saying those simple things will prevent everyone from not ever getting ill or having fertility issues, but I agree with you that the obesity problem is a big issue.