> Also (3) I don't get, because while I am extremely motivated by intellectual curiosity, I have maybe zero motivation to "develop my intelligence" like it was some kind of fitness thing.

I don't think of this in terms of intellectual fitness, but when I realise I made a wrong step in my modelling of the world I generally take a moment to reflect on where I went wrong and what I could do differently in the future to avoid similar pitfalls.