The Best Thing Since Sliced Bread

Someone just now wondered = what was so wonderful about sliced bread that created this saying:
"The best thing since sliced bread."

It occurred to me that almost everyone living today has ONLY known sliced bread.  And that they think that unsliced, whole loaves of bread are something special.

Well

Bread used to be sold as a chunk of bread and you had to slice it. It was kept in a bread box to keep insects and animals away, but it soon dried out and became very hard. (which is why bread pudding was invented -- to use up that rock-hard bread.)  

When Pre-sliced bread was invented, (plus wax-coated wrappers to keep it fresh), it was wonderful.

Have you ever tried slicing bread for a large group -- trying to make every slice even and the same as the others? 

Before I was married, I was handed a bread slicing knife (these had special edges to cut through tough crusts) and I had to prove I could slice bread properly in order to prove that I knew housewifely skills. 
I managed to pass that test only because our family loved Italian bread with our spaghetti and I had learned how to slice it evenly. (my brother and sisters would complain if one of them got a slice thicker than the other.) 

Pre-sliced bread was a Wonderful improvement. So, if something is the best thing since sliced bread -- It's got to be pretty wonderful.