Pi GPIOs - perhaps a silly question

Perhaps this is a dumb question and there are probably some really obvious advantages to using Konnected boards instead...but...

Wouldn't it be possible to wire an existing alarm system to a Raspberry Pi running Home Assistant and use the Raspberry Pi GPIO components https://www.home-assistant.io/components/rpi_gpio/ to connect sensors and relays for sirens? I.e. instead of using a Konnected board.

Sorry, I don't mean to be a heretic, just trying to understand why using the Konnected board is an advantage over HA on a Raspberry Pi directly connected to the sensors and siren (via a relay)...or what the issues with attempting that as an alternative might be.

Thanks for helping me understand...