I suspect your teacher never taught you reading skills and you muddled through somehow. Something similar happened to me on another instrument. The question of skills never came up until one day I realized I was missing a bunch of them.
.... Do you think you would have been open to this teaching *before* you hit a wall with your own muddle-through techniques?
An interesting set of questions, and you made me think.
I should clarify that this involved a different instrument. The major hurdle was technical, but since you played a single line of notes reading was less a challenge than for piano. For your 2nd question, I think so, because I came as a mature student who had played a number of instruments self-taught for decades. The idea of managing to play pieces was not exciting since I had done that; learning how to play and being taught by a real teacher was exciting. So when I was shown how to do something, I was interested, while my teacher's experience was that students find it tedious and "spared" me.
keystring, is there a different kind of teaching that could have gotten af your lacking skills, and taught them explicitly?
I know there was a more explicit way, since later I got exposed to that. I think it may also have to do with the proportion of time spent, and maybe what the teacher stresses that you should aim for, and maybe the pieces and exercises he chooses.
Addendum: I didn't really answer anything about reading music. (Came from a long trip yesterday). That was actually after returning to piano, which I had played self-taught as a child. By this time I no longer had a teacher, and I decided to learn sight reading and spent 10 - 15 minutes a day specifically on reading music. The rest of the time I tried to also work that way, making sure I was reading.