So I found this link that seems to have a more plausible explanation to why we need to check-in. It's an interesting read. TL: DR It's to ensure the airlines gets paid and is a continuation of legacy practices. I'm sure this could be handled in a better way to minimize friction for the passenger in 2024, however it probably helps airlines with upselling crap.

https://travel.stackexchange.com/que...-before-flying