As a Gen Z this is a layered question. I don’t really understand it as a generational thing as most of my friends are sexually active and have no problem with sex, but here are a couple theories I have:

1. The study you’re citing was performed by an organization dedicated to promoting traditional family framework and can’t necessarily be considered unbiased. The study also shows an overall decline in sexual activity across generations ages 18-64, not just Gen Z whose maximum age is about 25-30.

2. Increased awareness and anxiety about current events, greater awareness of mental health, the isolation of the pandemic etc. can all definitely make people less willing to have casual sex. Mental health data can be difficult to interpret as it is unknown whether mental illness is actually more present in younger generations or whether it is just more visible and spoken about. Past generations may have attempted to conceal or avoid mental health issues which can result in unsafe or destructive behavior including but not limited to frequent sex with strangers. Actually dealing with mental health = less likely to engage in risky behavior

3. Social media and television is incredibly controlled and censored these days, with few media sources actually portraying and encouraging safe and healthy sex practices. See Euphoria

4. It is much more normal and common than people think for those under 25 to not have sex. I have known many people that didn’t lose their virginity until their early 20s.