An embedded system project seldom has the need to introduce changes to the Yocto build system. Most of the time and effort is spent in application development, followed by a lesser amount in system development, maybe kernel and bootloader work.

As such, a whole system rebuild is probably done very few times. A new project is usually built from a prebuilt shared state cache, and application development work only needs to be done to perform full or incremental builds of a handful of packages.

Once the packages are built, they need to be installed on the target system for testing. Emulated machines are fine for application development, but most hardware-dependent work needs to be done on embedded hardware.