From my point of view, an owner-occupied property is not an investment, but a luxury good. I afford it not because of the financial benefits, but because of the advantages in quality of life.
I agree with you, if you optimize solely for cost and return, an owner-occupied property is not a good investment compared to a rental building. But, perhaps precisely because of the self-discipline you mentioned, it is a good piggy bank.
Just last or the weekend before there was a major report in the Süddeutsche or ZEIT about why today’s generation, despite well-paid jobs, can hardly accumulate wealth compared to their parents’ generation. Certainly, it is due to high social security contributions and late career start, but not least due to high consumption expenditures for cars, clothes, vacations, food, and much more. The previous generation saved on these in favor of building assets.
But I actually see it this way: even an owner-occupied property in a growth region is, for me personally, better than spending money exclusively on consumption. And you don’t have to live in it forever. Once the children have left home, selling the property is a good capital base for a rental building and retirement provision.