Sometimes, the way we drive keeps engine oil from being able to do its job completely and well. Short trips of only a few miles and lots of stop-and-go driving can cause particles in the oil to become deposits in the engine, which can build up over time. These deposits restrict the flow of oil.
An engine flush can clear out those deposits to open narrow oil passages clogged by gunk that's been floating around in the oil. Releasing those deposits and allowing the oil to flow freely saves wear and tear on the engine and keeps parts moving as they should.