I had it once and I wasn't really a fan either, but then again I also don't really like tea in general.

Like with a lot of things, some foods and drinks are "indoctrinated" to us as children. I imagine mate falls into this category.

Could also argue coffee and alcohol taste horrible at first, but you learn to suss out the more complex flavours with habitual use. Of course you also learn to enjoy them because of the effects they have on your body.