system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do I need an ISP to connect to the internet?

ISPs seem to be gatekeepers to the series of connected networks we call the internet. Why can't we all just have our own individual gates?
gpt
For the same reason we can't all have a private road to the airport or that restaurant we like.

If the airlines are the huge, fast pipes that form the backbone of the Internet, and your LAN is a gated community, the ISP runs the trams connecting your community to the express trains (which may or may not also be run by your ISP) that go to the airports.

It wouldn't make sense (or be possible) for everybody's driveway to lead directly to the airport because you don't always want to go that far, and it wouldn't make sense if every house only had a gate to their neighbour's garden because that would be terribly slow if you need to go further than a few houses over.

So you pay an ISP to connect your house to his network of trams and trains that connects to other rail and air networks, effectively connecting you to the whole globe. 

You could arrange with your neighbours to go through their gardens until you reached a nearby tram stop instead, but not everyone is comfortable giving their neighbour a key to their garden gate.