The only real reason for "Rev Matching" is to match the engine speed with the transmission speed to avoid locking the drive wheels. I do rev match often when driving a car with a manual trans mainly from habit being it makes for a smoother engagement between the engine and trans. If you are good at rev matching you dont even need to use the clutch, not that I advise that. If you match the engine/trans speed exact the shifter will slide right into gear without the clutch, and this does absolutley no damage to anything. This can be helful if your clutch blows or the cable snaps etc...