We believe in evil eyes because some people always watch other people & cann't bear their happiness, so they always try to harm other people, So, is it necessary to gift them red bordered black goggles or finallly scratch & destroy their eyes , so that they couldn't do it again.
I defined evil eyes as the eyes of person that only harm others, You should understand the meaning properly!! The people of ancient world had the concept that evil eyes means , this eyes immediately harm people when they see something but in present world it's mean the eyes only want to see others sadness, cry, loss, they only try to see they are the most happier people in the world & they spend most of the time in harming people.
So first you need to understand the whole , then try to answer it.