The initial disorientation from an attacker's first strike would make it difficult to assess what was happening quickly enough in order to engage in an appropriate defensive behaviour before being struck again and then repeatedly. People that have not been trained to receive landed punches are generally not well-equipped to handle them, and attacks can happen lightningly quickly - before you know it, a person can be upon you, levying a series of blows that have left you injured.
Your assessment is spot on. This is my greatest priority in studying martial arts. That is training at point of failure. Too often it gets dismissed as "well what can u do about it", or " just don't let him do that", or " train to prevent it from happening", or "budo is not about this". Etc.
I spend most of my training in this mode, that is, my opponent, assailant etc has the tactical advantage and I need to mitigate this, recover, and put myself back in control.
Those that dismiss this or fail to address this aspect typically do not understand fighting and/or do not have the ability to teach it, so therefore they don't emphasize it.
it may also not be your thing either and you are doing budo for another reason, I'm good with that as long as u are not giving flippant remarks concerning the importance of addressing this important dynamic in a fight.