The way you are configured, your biology does not really mandate you to be attentive. You can go about life even in inattention; you can continue to live even in inattention. Attention, therefore, is not really necessary or compulsory to continue living biologically even.
If you have no attention, then you might still live for seventy years. Therefore, attention has to be practiced. It will not come naturally or biologically to you; it has to be a thing of practice. Biologically, all that comes to you without practice, without any kind of effort, are your biological tendencies.