system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why has the video quality of Skype and similar applications remained relatively poor even though residential internet speeds have increased exponentially in the last 15 years?
gpt
Short answer: Skype uses real-time unbuffered (mostly) 2-way video without a content delivery network.

When your computer receives anything from the internet it is divided into lots of pieces. At any point these pieces can be lost or delayed and your computer has to request them again. Even on a good day many pieces of data will be lost because of all the complicated things that happen along the way.

If you're watching buffered video, like Netflix, these lost pieces of video don't matter so much - your computer has time to re-request them and stay on top of things. Usually it can even catch up for lost time during moments of good connectivity or low bandwidth video. Skype is different - there's no use in showing you a bit of your sisters face that arrived 5 seconds late, it's either now or never. So what Skype does is ignore missing pieces and try to make the best of what data it has. This will mean some lower quality video.

Then there's the content delivery network. Sites like YouTube and Netflix realise that many people are watching the same videos. To make things faster they distribute these videos on servers around the world in advance. This means you get the data faster and therefore there can be more of it - meaning higher quality. Skype can't do this because.. it's being recorded as you speak.

Finally there's the fact that Skype is mostly 2-way. Not only are you watching a video, you are also sending your own video. Technically this shouldn't make a difference because your internet connection separates incoming and outgoing traffic. In reality it's more complex and your computer is more likely to struggle, it has to 'encode' video - in real-time, and deal with extra network traffic. On top of this, your internet connection is usually slower at uploading than downloading. That 50 megabit connection you were sold is _probably_ only a 50 megabit _download_ speed.