Why is API KEY needed when the same information can be obtained in HTML format?

Question

API

The site has a map with buses moving along it, there are temperature sensors.
The site has an API. It gives the same information as on the site, but in JSON format.
And they made an API KEY there.
I wonder why? Is it fundamentally important to put the Key on all APIs?

Answer 1

This is how you identify your application. If they do not impose any restrictions on the number of requests on the API, then what's wrong with that? They have statistics and you have an API.