This is often used by players in the Grand Exchange, where a trade offer quickly disappears in the volume of other messages, or used to advertise a real world trading site.
Autotyping programs can be used to repeat a specific message over and over.Typically, they are used to perform tasks deemed overly tedious by real players, such as training a particular skill, collecting a certain item, or quickly typing an offer or phrase. Macros can be programmed to perform almost any task. Notice how they walk away as soon as the tree is cut down. Several macroers chopping down a yew tree.