The insert style is so that you can have the compressor react to all the information in the signal, but with the bass filtered out so it doesn’t kill your kick:
You can do it the way you describe, which is to not send the kick through the compressor at all, and instead make the compressor react to the kick information, but acting on the buss signal. That’s more the conventional way of doing sidechaining. In that setup the buss is generally not really being compressed, except when the kick triggers it, hence ducking it to allow more space for the kick.
The method with the insert & filter allows for buss compression of the signal (to increase overall level) but without the kick & bass energy causing the compressor to over-react.