system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] Jarvis is uploaded into Vision and has to be replaced by Friday. Who's defending the missile codes from Ultron now?

Did Ultron just give up once he decided to drop Sokovia? Awfully lucky.
gpt
Just because Jarvis was uploaded in to vision doesn't mean Jarvis couldn't exist simultaneous in the internet, he is a computer program and could exist in multiple places at the same time the same as ultron. 
We do not know why Friday was put in to use. Maybe necessity, maybe to avoid confusion, or maybe Stark felt uncomfortable using Jarvis after putting him in vision.