@RustyStriker People don't want a partner because they are an outlier. Less than one per twenty people I have met (<5%) would prefer to be single.
People don't want children because it is a huge responsibility that is, again, not all sunshine and roses. The more convenient life is with more and more dependence on external assets such as the supply chain, technology and government; the more weak the modern person becomes. Most people are too incompetent to raise a child and it would cause more harm than good for their well being.
There are unfortunate outliers in every model, including the ones that took their own life in modernist&individualist countries where suicide rates skyrocket.
It is not all sunshine and roses, but it paints a more complete picture of a life, to have a bond with a significant one and raise a child; than not sharing a strong connection with any one else, staying as an individual.