Look, this may be stretching the definition of conceding, but I've realized something. We left out details of the fact we were on the verge of death. Who's to say Kyoko doesn't call us on the fact we were stupid enough to contract with full knowledge of what it entailed? Which might mean going into our wish. If we were the Saint/Martyr/Professional Altruist/pick your term for what we want to portray ourselves as, why would we wish for personal power on the verge of death? Which would mean something about the wish is incredibly important to us. Worst case scenario, this could lead to the inference that Grief Seeds are literally necessary for the continued survival of Mahou Shoujo. Not saying my previous vote is any better in that regard.
The best answer I can come up with for that is analogous to the reason Dresden picked up Lasciel's coin. To keep one of Michael's children from picking it up. After all, Sayaka and Madoka don't know enough to optimize a wish properly, right?