It's a tragedy of the commons combined with selection pressures. If there is just a few people who decide to spread out and make as many copies as possible, then there will be slightly more of those people in the next generation. Those new multipliers will copy themselves in turn. Eventually, the population is swamped by individuals who favor unrestrained reproduction. This happens even if it is a very slight effect (if 99% of the world thinks it's good to only have one copy a year, and 1% usually only makes one copy but every ten years has an extra, given enough time, the vast majority of the population has 1.1 copies a year). The population balloons, and we don't have that tremendous wealth per captia anymore.