Why do people put personalized license plates on their cars that no one else understands except them?

I was driving today and a vehicle in front of me had a personalized license plate that read “YGENIK-LUV2”, then further down the road, I came across another car that had a license plate that read “GOOD4-SMITH”. I know these personalized license plates mean something special to the vehicle owners, but if I or anyone else driving behind them don’t know what the heck they mean, why even bother displaying them publicly? It doesn’t seem to make any sense to me, other than self-gratification that serves no real purpose. Why do people personalize their license plates with messages that are meaningless and non-sensical to other people?