Star wars was the most common game that had a yoke.
Color vector games have a HUGE rate of monitor failure. A replacement monitor (which can also fail at any time) costs almost as much as the game is worth.
Star Wars machines were not very likely candidates for conversion. Wierd controls, vector monitor, etc, made them likely to just sit in storage rather than get that new Final Fight kit.
So, with 12695 Star Wars machines produced, and perhaps 500 working monitors left, that leaves 12195 yokes to get sold off.
Also, on a related issue. I have no idea why Atari vector boardsets are worth anything at all. Almost all the Atari vector games had huge runs, and defective monitors, the monitors are the problems, not the boardsets.