A Vectrex wasn't prohibitively expensive, but, even for its time, vector graphics seemed a bit primitive*.

1980s TV gaming consoles may not have had high resolution, but they were less visually monotonous than glowing lines on black.

* Consider that Asteroids is the only vector-based game listed here: https://en.wikipedia.org/wiki/1982_in_video_games

** https://en.wikipedia.org/wiki/Asteroids_(video_game) was already three years old by the time Vectrex hit the market