I think the main appeal is to work with small devices that have well defined resources. Just consider the popularity of the ATtiny85.
However, low end 32bit devices are also available from reputed suppliers. In fact, STM just announced the STM32C* series which is also aimed at replacing 8 bit controllers.
The cost benefit may only be true for low numbers and when sourcing from distributors. I am fairly certain that the price advantage is much less when talking about actual production volumes
Generally the newer STM32s are easier to find because, I assume, they aren't being snatched up by the billions to make designs that were finalized well before these chips were released. I didn't have trouble finding STM32G0 during the height of the shortages.
This is the problem when building around a specific part, no matter how cheap. The hobbyist community has selected certain daughter boards to clone, and then place SoCs on them that can run Linux (or any other hobbyist OS). If one SoC vanishes from the market, you can drop another one in, and often with zero changes to your design, keep going.
However, low end 32bit devices are also available from reputed suppliers. In fact, STM just announced the STM32C* series which is also aimed at replacing 8 bit controllers.
The cost benefit may only be true for low numbers and when sourcing from distributors. I am fairly certain that the price advantage is much less when talking about actual production volumes
*https://www.st.com/en/microcontrollers-microprocessors/stm32...