Imagine that there passed an international law that illegalized the ownership of private cars, and enforce people to use only public transport.
of course this is good for our environment and to reduce pollution and reduce consume of oil energy.
But this will be very strange law, many people will complain and motor industry will protest this law.
But may be in the future there will be such a law that prohibit using private cars, maybe because people became more aware of their environment, and for one who travel in time machine in the future will find such law strange.
Now people who wrote religious books, they found slavery normal, and successful industry, so they cannot stop it, it’s just like owning a car in these days so why bother.
Some religion like islam go further and make slavery motivate to it’s idea
And that is how:
“Certainly will the believers have succeeded”
“And they who guard their private parts”
“Except from their wives or those their right hands possess, for indeed, they will not be blamed –“ Quran 23:1 23:5 23:6
Right hands possess means the slaves, so you can have sex with your slaves, but suppose that you do not possess slaves and you do not have money to buy?
The answer is : go fight and kill husbands and claim the wives, and this will not considered rape or war crime because it’s not a crime to have sex with who you possess.
By the way wives limit is four, but you can possess as many as you can.