Why serve 1x1 pixel GIF (web bugs) data at all?

Question

Many analytic and tracking tools are requesting 1x1 GIF image (web bug, invisible for the user) for cross-domain event storing/processing.

Why to serve this GIF i

Answer 1

You don't have to serve an image if you are using the Beacon API (https://w3c.github.io/beacon/) implementation method.

An error code would work if you have access to the log files of your server. The purpose of serving the image is to obtain more data about the user than you normally would with a log file.