I really, really don't understand why these simple-ass microcontrollers are running proprietary software instead of something open source like ESPHome or Tasmot

I really, really don't understand why these simple-ass microcontrollers are running proprietary software instead of something open source like ESPHome or Tasmota. There is no added value in the proprietary software running on an MCU with a sensor, it is all in the service that run on top of them. It infuriates me that all these perfectly fine devices now are junk, because some clown decided that they needed to develop their own "platform".