The biological need to have your testicular temperature lower than 25 ΓΒΊC for male fertility. This temperature in required for the process of sperm development, or spermatogenesis, to proceed normally. The testicular blood supply is also specialized to help maintain a lower scrotal temperature.
"STILL, MANSPREADING IS WRONG"
But that's why we have our testicles out of our body and not inside...
"WHAT ABOUT IT, CIS-GENDERED WHITE MALE"
29π 12π