I abandoned my first draft for this topic. Let that concept be the overall theme.
Short answer: why not? Long answer: biology, ego, and habit.
We are chained by the rules of our biology. We have fundamental and insatiable urges. Earthly pleasures like food, sex, happiness; we just can't have enough of them. We always need more. We crave acceptance, money, romance, and adventure. And our fundamental fears tether us to our desires. Fear of death, loneliness, poverty, pain. We trip over ourselves running from our fears, fighting them off, or dashing toward pleasure. That doesn't mean suffering doesn't exist. Just that we are conditioned to get around it. But is that better? What can we learn if we don't struggle through our problems? A baby learns to walk by observation, intuition, and perseverance. They would never stand if they hadn't struggled.
Humans are not as separate as we've conditioned ourselves. Everything is not so different. We all mirror one another. As above, so below. Morals are something we've created. The ego keeps us trapped in our heads. Expectations can never be met. We believe our thoughts make us who we are. Our flesh and spirit allow for many other senses, yet we use our thoughts more constantly than any other. Therefore, we end up forgetting to sense the world around us. We're stuck in our heads. There is no good and bad. Everything is grey. We have rules to ensure that we adhere to labels. We label to make sense of things. Nothing makes sense. Instead, all that is simply is. When you accept everything as it is, there is no need for a "self." There is only us.
Suffering is the result of resistance. Whether we choose to resist our biological urges and desires or our spiritual destiny, we will suffer. Mastering the delicate balance between them is the key. And it takes practice. We've developed habits that keep us stuck in fears, judgements, and duality. There's not a devil and an angel on your shoulder yelling over one another. Humans all have one voice together. So we must be kind to ourselves. When we are kind within, we can be compassionate to others. When we heal ourselves, we heal others. Suffering becomes neutral in love.
So suffer away, my friends. I'm suffering with you. Life is hard. The level of difficulty doesn't negate life's value. We are meant to experience this life in this way. And we are meant to do it together. Teach me your ways.