Because of, and no disrespect or to step on toes, it's because of their pursuit of doing works to stay in good standing throughout their life, and confessing every wrong committed......which is impossible.I really, really hesitate to get involved here, and I'm not going to debate it, but...
Both the Catholic and Jewish faith (notice: both are not "Christ believers") teach that your body does not belong to you. It belongs to God.
The Catholics go one step further, and teach that your life is not yours to start or end. It belongs to God. Hench the Catholic teaching that suicide is a Mortal Sin, stopping one from achieving Heaven.
The only thing you own is your free will.
"He made them in His image."
Which is translated by both religions to signify that your body is something holy. Hence the Jewish proscription against tattoos.
I have never prescribed to either view, but that's probably one of the many, many reasons why I'm an adherent to neither religion.