There have been plenty of projects that do send junk data to these endpoints. The problem is the junk data gets users noticed because some manager looking at dashboards gets an alert about some supersonic Corolla driving down the Pacific. And they go yell at the team responsible.

As a result, analytics endpoints generally have some authentication and verification built into them. Obviously, with enough time it's possible to reverse engineer these components. But that's a lot of time and effort vs just blocking the request.