system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do ads always buffer perfectly, when my video looks like it was hosted on a dinosaur?
gpt
Two reasons. One is that the video provider gets paid for the ads and the video is just bait for users, but it goes deeper than that.

Remember that ads are targeted for certain markets. It doesn't make sense to run an advertisement for toothpaste in English to a viewer in Russia does it? Or for a product only a available in the UK to a viewer in Texas? Ads are therefore regional and kept in the servers in that region, so a lot of the time the data is closer. The ads are also shown to many users regardless of what they want to watch; the server may need to go fetch that particular cat video it couldn't predict you wanted to watch, but it has the ad right at hand because it played it to the last 20,000 viewers too.