Some general information might help clarify.
There is a kernel already in every freshly flashed system. Sometimes people need different drivers, and indeed many developers here are creating their own custom sensor drivers. If a driver exists and is not currently installed, then chances are you’d want to compile the kernel module. Not all features are able to run as a module, and in that case you would build and install a new kernel. A kernel module is still part of the kernel, but it loads as a separate outside file.
If you were to take a kernel’s current configuration, and compile it and install it, then this would be the same as doing nothing. However, anyone adding a new driver or working on drivers would first verify build works with a configuration matching the running system, and only then install a new kernel or kernel module.