I didn’t discover the joy of mayo until late in life. I was always a ketchup girl myself – ketchup on burgers, hash browns, sausage, etc. It was the perfect (yet unhealthy) sauce to sate my sweet tooth when eating meat and potatoes as I was growing up.
Mayo has a much more subtle flavor and goes well with such a greater variety of foods. Also, so many amazing sauce derivatives use it is as a base; I never realized how often I was eating it and just calling it something depending on one or two different ingredient from the standard.