Man is naturally lazy, they need a push to get anything done. Some things are left the way they are, because we have not get the push needed to get it started. Most times this push comes when the harm as already been done. Man's creativity is at it best when he has been pushed to the wall they say.
If not now then when? This question should be programmed in our heads to always remind us of the question whenever we are about leaving something that should done immediately for latter date. May be, just may be humans can be proactive in solving their problem before it harm them. Even though I believe humans are so complicated that, even with that, the human habit of procrastination cannot be solved with the repeated above question in our heads. The alarm clock was provided to give us a sound reminder to do a particular thing at a particular time, but yet, we choose to hit snooze button. That is humans for you.
There used to be an exposed electric wire in our house where the switch to the bulbs are. The exposed electric wire had been like that for years, I have thought of covering the exposed wire countless times, but never did. We all knew the danger of it as it was easy for any to be electrocuted since the exposed wire was right at the place where we do touch every day. But no one among us in the house covered it even though we have thought of covering it many times. We covered it the very day the wire electrocuted our niece, and was hospitalised for two days. It was like we were waiting for the wire to shock someone before we can cover it. That's humans for you.
If not you then who? ; As I said earlier, that, humans are generally lazy, any opportunity to push a burden to someone is quickly embraced. It becomes a problem when everyone thinks it not his responsibility. And when there is no one to assign the duty to someone. If you are not the one to do it then who? This question can also be a resounding reminder in our heads to take responsibility even when not assign to do it, for the betterment of all. I can remember back then in my primary school, if the teacher comes into our class and says, someone should sweep the class, I bet you, he will come back and meet the class dirty as he left it. But if he mention the names of those to sweep the class, the sweeping will be done in no time. That is so, because humans are lazy and won't not want to take responsibility except forced to do so. This brings us to the question, can Humans be rational to do the right thing without been forced, whether by law, power, or nature?
I don't think their is any better explanation, but to agree that humans are naturally lazy and must be forced to do even that which is benefits to him.