Q: Why do we watch things “on” television, but we watch them “at” a movie house and “from” the balcony of a theater?
A: English has an incredible array of prepositions, and it often seems that we have far more than we need!
Generally, when we talk about the place where we do the viewing, we use “at,” as in “I watched the movie AT home … or AT the movie theater … or AT Jennifer’s.”
When we talk about the medium on which we view the movie, we generally use “on,” as in “I watched it ON my new flat-panel TV … or ON DVD … or ON film.”
When we talk about the position from which we watched something, we usually use “from,” as in “I watched FROM the 50-yard line … or FROM the third row … or FROM my armchair.”