I used to play in wrong keys because of how I first related to music. I was introduced to movable do solfege when quite young, and it was the only thing I knew. I then taught myself to play piano and a few other instruments like the recorder as a child, and from notation, but I read that notation still according to solfege. So I would "find Do" --- in G major that Do is G; in D major that Do is D etc. - and hear and play everything from that Do, hearing my major and minor scales, intervals etc. Consequently, I might start the music in the wrong key, including when looking at the notation, because Do is Do is Do is Do. Since I was untaught most of my life, how I ended up relating to music is an anomaly.
I have been improving my ability to read music, and doing it in a real way, for a number of years. I discovered recently that I am not that aware of whether a note is on the 2nd or 3rd line, or how many ledger lines there are altogether, because a lot of it has been so intervallic. If you go up 4 from Sol to the next Do, it really doesn't matter what line and space that Sol and Do are on, because you are also hearing the whole thing. It is a different wiring.