It’s just an empirically observable reality.

Religious people tend to be less lonely , more likely to be married and have children, and more happy and less likely to experience mental illness, on average.

It’s certainly not true for every religious person nor the opposite for every atheist, but the effect can be seen across populations.

It's also demonstrated that meditation and volunteering improves well being regardless of beliefs... and atheists like myself have no excuse not to be doing those things right now.