In an environment where total wealth does not grow the only way to get ahead is to take from someone else. Therefore, in an environment with a fixed supply of resources, respecting the rights of others is a strictly worse strategy than taking what you can when you can. It is only in a growing economy where two people can interact cooperatively and both come out ahead. We see this truth in comparisons between human society and the societies of other mammals. Male lions brawl with one another; whoever wins devours any children that don’t carry his genetic material. The animal world has no morals. In the zero-sum savannah this is perfectly rational. Any food and territory going to them is food and territory that isn’t going to your bloodline.
Since at least a few centuries ago things have been different in human society. Growth of what were once rival clans becomes mutually beneficial because it creates more vectors for trade, a bigger market for specialized goods and services, and more chances at transformative innovation. The possibility of positive sum interactions is the foundation for all moral behavior. We have not had this possibility for long and we do not yet fully appreciate its importance. If our society ever stops growing, it is only a matter of time before we return to our deep and brutal evolutionary roots. So, even if you still adhere to Rawls’ principles of justice, only a dynamic and growing economy will produce the incentives necessary to uphold them.