This is a really good question. Clearly, God knows us, our level of faith and the potential we have to serve Him. Further, in the mind of our omniscient God, He can see the full landscape of time and how each of His servants can be used in that plan and purpose.
This has been a long-debated question. Some have suggested that the Apostle suffered from malaria symptoms, poor eyesight or a speech impediment. While these might be reasonable assumptions, it doesn’t seem to fit the context of 2 Corinthians, where Paul is frequently addressing the false accusations and actions the Jews.
In Genesis 3, we are told (as is referenced in Genesis 8:21) that the curse of the ground, which included the production of thorns and thistles, was for his sake. Production of food in the Garden was now quite different outside of Eden.