Because it's fun.
I choose to go through the LeetCode. I choose to go through the LeetCode in this decade and do the other things, not because they are easy, but because they are fun, because that goal will serve to organize and measure the best of my energies and skills, because that challenge is one that I am willing to accept, one I am unwilling to postpone, and one which I intend to win, and the others, too.