I agree completely. Taking a shower, brushing my teeth and other routine things have never become a habit for me either. I have to put in the same effort every time.

Of course there are habitual things in my life, but I can see no common characteristics. Total time spend certainly isn't it.

Amusingly, this has made it almost trivial for me to quit smoking despite being a smoker for many years. I just never developed a habit for it, so dropping it was as simple as just not smoking.