In a different question around a specific microcontroller (ATtiny12 - datasheet) I came to ask myself: What are the intended use cases for such devices?
Does it target the segment: Too "complex" for a small PLD/CPLD and too "simple" for a FPGA/"conventional" microcontroller?
I have problems coming up with use cases to form a better picture of this type of microcontroller in my mind.
If you have used these devices, what for?
What is the intended use case?
Why not use an 8-bit controller with RAM in a, e.g., 8-pin package, or maybe even a 32-bit core controller in a 10-pin package (seen those)?
What should it not be used for, besides "fitting the bill"?
As so many answers were given and the question was of rather "open-type", i would like to do a summary:
These Devices are used in high volume, low complexity designs were cost is a prime objective and dedicated ASICs do not exist or are too power hungry. (Remotes, Toys, Tactile/LED HMI)
For low power applications or stand-by operation blocks of a design. (SMPS, Stand-By with main controller powered down)
For mid-volume applications were cost is sort of an objective and the required functionallity is not available in a ready-made ASIC. (E.g. ADC sampling with some math and giving an ISR to a controller in sleep-mode)
I also deduced that, if not only cost, but also time-to-market is an objective, these devices can be used to implement low complexity functionality faster compared to a "custom ASIC".