Like most people, I remember them being sold at Woolworth's and have always thought that, theoretically, they should be much more common. After all, didn't every small town used to have a Woolworth's before Wal-Mart arrived and forced them out of business? Also, they were sold by Sears (as "Road Mates") and other discount chains (under the name "Fast Wheels). I can't explain their absence: they don't seem to suffer from metal fatigue (like some other Hong Kong brands) and destructive boys couldn't have burned, "hammered" and "firecrackered" them all out of existence. My theory is that their scarcity had something to do with their price: they were priced relatively high for an "off brand" at $.99 in the late 1970s. Hot Wheels cost less than that at the time and so did Matchbox as a general rule. Additionally, they were well-established brands that young consumers readily identified with due to massive advertising campaigns in both print and on television. I can remember as a kid that nobody wanted Playarts; when I would get together with my friends to trade cars, I always offered up Playarts (sometimes as many as three for one) to get anything Matchbox! While they might have been nearly an equal to these other brands on several levels, the perception among 1970s boys was that Playarts were ugly, clumsy and inferior. Perhaps a combination of these factors killed them: they cost too much and they weren't well-liked by kids. With the arrival of Hot Wheels, everything changed in the diecast market and accurate scale models (like those offered by Playart) simply couldn't compete against the more fanciful Mattel products with their futuristic styling and wild colors. Matchbox and Corgi responded by introducing absurd models that completely missed the mark and alienated their traditional customers; Playart never did this and it was probably just as well since the battle was already lost.
Playart also produced a range of larger scale models that hovered around 1:43. I've also seen listing for models that were supposedly 1:32 and some others, mostly buses and fire trucks were scaled around 1:87. Apparently, none of the larger scale items sold well since I have seen liquidators still closing out new-old-stock as late as 1996. Again, they made a Range Rover at a scale of 1:48. I think there was also a Fiat X1/9 and a Toyota Celica and three others for a total of six. The 1:43 scale models were sold both with and without friction motors. The 1:48 scale Range Rover I have was repackaged as a "Model Power" toy and certain others were as well.
Here are the last eight Playart models in my collection.