Landline calls, at least when I was younger, were not disconnected until the caller hung up. I assume there’s a technical reason involving channels instead of packets but I never researched it.

Landline calls were disconnected after a timeout. The receiver could hangup and pick up quickly and still be connected. We used this method to move to another phone in the house. Also if you tapped the hook a few times the line would disconnect

Technical reason was mechanical exchanges (Strowger etc) https://www.youtube.com/watch?v=xUOh9fCSgqw

implementing logic/timers with cogs is impractical.