We had children because it is a very essential part of being human and it gives us someone who is very much part of us to care for and who cares for us. Children are also a lot of fun. Nothing funnier than watching a toddler play or eat. Nothing more rewarding than helping that child learn and grow to become a contributing member of society.
Children can be difficult, tiring, a huge financial strain. Bit they are almost always worth every bit of it and then some. They can also give us joy, love, a sense of pride and accomplishment. Life would seem kind of empty by comparison.
Hope this helps.