Why is it that so few people understand Sarcasm?

Sarcasm in a newer thing that apeared around the 1970s or so and people don't all the time understand, for instance if i sent a sarcasic text like "your mom" the person can't hear my voice and don't know if i'm mad so they may get confused and very offended. this happened a few days ago and so i would not recomend using it.