I think I may make an independent thread about this soon (but my question may be stupid): why does messages use this paradigm of connecting to one's phone direc

I think I may make an independent thread about this soon (but my question may be stupid): why does messages use this paradigm of connecting to one's phone directly instead of accessing texts in some centralized fashion? Is that impossible because only the carrier has the contents of the thread (even though other services can be used to post texts)?