Surely, it's a case of whatever works best? And we are all different. Each to their own? If you suddenly decide to change something about yourself but New Year's been and gone, sure, you might as well start straight away. But there's nothing wrong with waiting until New Year if you make your decision late in the year. If it helps you focus.
I might go to the gym in the New Year. Hardly a resolution and I do love / miss going to the gym. I hardly need to go and it would hardly be a resolution but if it helps me focus / motivates me (setting Jan 1 as an all-important start-date), it's hardly a problem.
I quit smoking Friday 13th of October. The date had an easy to remember significance (though I'm not at all into superstitions / stupid traditions). I just liked the date so that I could easily check against the progress I've made without having to keep a record on a calendar / in a diary (not exactly difficult to do, but I don't bother with either).
So, whilst I admire your sentiment, I can't really say I agree with your view. Interesting post, all the same. :)
Thank you @zool237 for this detailed comment. yes, you are right when it helps to focus you it's a good thing.