ShiroKuro I think this is perhaps one of the most important activities one can do to develop sightreading ability. In other words, over time, active reading of known pieces contributes to the ability to sightread new pieces, i.e., to play through a piece of music you’ve never seen or only seen and played a few times.
My thought as well. I don't practice sight reading per se, but I do actively read and over time my ability to pick up a new piece and "read" through it has increased; with increased ability to read new pieces, my speed of learning those new pieces has increased. I don't see myself picking up a piece I've never seen before and playing it in front of somebody--there are people who do, and more power to them--but it's not something I see myself doing. What I do see as the benefit of better sightreading/reading is making it easier to start new pieces at or above one's level.