I love bags. They are, to me, the perfect blend of form and function, and I have several.
I always have one near me, and keep all kinds of personal and 'essential' items in it. I like knowing that the things inside it are easily accessible (I'm not otherwise very organised), and they give me a sense of security and privacy.
Growing up, my mother had no boundaries when it came to allowing my sister and me to have what she would have called 'secrets', and I took to putting personal items into a handbag and keeping it in sight at all times. That habit has persisted, although my husband wouldn't dream of violating my privacy (and I have no 'secrets' from him anyway.
On the rare occasions that I go out without a bag, I feel stressed, and it is almost certain that I 'need' something that has been left behind - a pen, a tissue, lip salve - whatever.