Train the way you carry, and carry the way you train.
Most of us live comfortable middle or upper class lifestyles. Danger is simply not lurking around every corner.
Nonetheless, we carry because we know -- and it has been demonstrated -- that even the upscale mall or neighborhood which "feels" safe, can be violated without notice.
Carrying chambered requires absolute discipline, rigid training, and a strict manual of arms. The gun may be safe while on your person, but it is an ever-present danger while off your person. Where is it when you are in the shower? or in bed? or out washing the car? When the gun is removed do you lock it up? or clear the chamber?
Every moment that chambered weapon is off your person is exposure to Murphy's Law. You need to get it right 100% of the time, all of your life. Murphy only needs one chance to wipe out your lifetime perfect record.
Some gun owners may not have the opportunity to adequately train for chambered carry, or may feel they lack the discipline required. This is not to be mocked; it is a demonstration of sound judgement, and understanding of their limitations. (Certainly, all of us can think of one time when we did something stupid with a chambered weapon.)
However, considerations regarding response time and the likelihood of losing the gun to an assailant are valid. I would encourage proponents of non-chambered carry to reconsider their commitment to training. Training will bring more confidence.
Additionally, that gun is meant to protect your loved ones -- buy one with multiple safeties protecting the chambered round (trigger, drop, striker). The fine choices available leave no excuse for a cheap, unsafe gun.
In any event, train the way you carry, and carry the way you train. When the threat strikes, you will be surprised and frightened. Blood is drained from your extremities and rushes to your core organs. Clear thinking will be difficult, fine motor skills are degraded and simple procedures (racking the slide) will become complex.
Your success will depend on learned habit and muscle memory. Everything you do sloppy in training, you will do sloppy during the threat. Everything you do right in training, will support you facing the threat.