Actually, the first question is “Do I need to change my transmission fluid at all?” For the answer, consult your Hyundai Owner’s Manual. Unless there’s a leak or a problem, some newer transmissions are designed to never need a fluid change.
But let’s say your car does need a transmission fluid flush as part of preventive maintenance. The top reason to change it is to keep your transmission operating at its best. Like any other fluid such as engine oil, transmission fluid becomes less effective over time. Stop-and-go driving, towing or other high-stress conditions can shorten its life even further. Unlike other fluids, however, transmission fluid doesn’t just lubricate the transmission parts, it also acts as hydraulic fluid, helping keep the transmission cooler and helping with shifts.
In a practical sense, the most important reason to perform preventive maintenance on your transmission comes down to dollars and cents: getting a transmission fluid flush might cost you a few hundred dollars, but a new transmission will cost thousands.