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

Well the major reason is to attach the cookie to it so if users go from one side to another we still have the same element to attach cookie to.