A revert may be done for a wide variety of reasons, including: fixing errors introduced by previous edits; restoring the material to a state that was not contentious until new disputes can be resolved; undoing scope creep; regression testing; and even petty malice, vandalistic intent, or personal unhappiness with the author of a previous change.
A revert can be done for various reasons, such as fixing mistakes made in previous edits, returning content to its original state before conflicts arose, stopping the expansion of work beyond its intended scope, performing tests to ensure that changes haven't caused problems, and even undoing changes due to malicious intent or personal dislike.