Who says you can't judge a book by its cover? You and I and we do it all the time. What else would you call it?

Maybe some people do...I personally do not and believe most do not. 

The bigger question is why do we judge a book by its cover?

It's the first human attempt at advertising Rosie....When writing was first invented....I believe that Religious books were the first to go to print In one way or another...
It was passesed on to uneducated people by the rich and powerful as turned out to be the most wonderful way of feeling nonsense to the masses...it then exceeded all spectations after people were forced to read and write..l

The first schools in England only had two subjects that were compulsory education way back then.....The most important was religion and putting the fear if God in to young brains that were empty and knew no different...
The other was physical education to make Boys strong enough to fight in the Crusades to spread the word of evil nonsense and to set man agains man so certain countries could steal their lands and take people in to slavery and get some well needed free labour for their new owners...