Lots of “smart” products come with BK7231x chips that are flashable to esphome, nobody needs another custom protocol (even if open) since esphome currently supports local encrypted transport that’s going to be better than 99% of what the Chinese (or even western) companies are going to design for local communication.

Oh, and hobbyists mostly aren’t going to pay premium for those either, unless those come preflashed with esphome and sponsor hass project, and even then 90% people are still going to buy the cheapest option on the market:)