[old_tv_nut]

They went looking for a prop, and that is what they found. Remember that movie studios were originally very antagonistic to TV, and the people working on the film probably knew next to nothing about real TV studio equipment. Strange and inaccurate depictions of TV exist in most early movies that have TV incidental to the plot. Even if the film people knew better, there was no need to be realistic, as it was irrelevant to the plot and the movie audience didn't know what it should look like anyway.

Edit: I looked up the date of Ice Castles - 1978. Didn't realize it was that late. The film crew certainly knew what a real monitor looked like by then, but obviously used the most expedient prop.