The plastic knifes are much more useful than steel knives when for cutting hot, moist bread that was just removed from the oven. For some reason, fresh bread sticks to a stainless steel knife, even when the knife has been dipped into butter or oil. However, the bread does not stick well to a plastic knife, especially when dipped into oil or butter. Therefore, after baking fresh bread, I can take fresh bread directly from the oven and immediately slice it and eat it. I don't have to wait for it to cool down.

In the photo below, I am holding a piece of my freshly baked bread in a napkin because it's very hot, and as soon as I start to cut it open, steam will come out of it. I am dipping the plastic knife into a small jar of refrigerated olive oil. 

Incidentally, the flexible plastic knives are excellent for spreading butter, refrigerated olive oil, mayonnaise, and other soft items onto bread. 

The series of photos below show how quickly and easily this plastic knife can cut through this hot, moist piece of bread. I can slice and eat my fresh bread within seconds of baking it. I don't have to wait for it to cool down.

 
 

 
 

 
 

 
One reason I like using plastic forks and spoons is because they don't make much noise when they contact porcelain or glass. Some people like to eat dinner while music is playing, and I suppose they don't notice the noise that the spoons and forks are making, but I prefer eating dinner in a quiet environment. I prefer television or music before or after dinner, even when I am eating alone in my own home. When a dinner is made with excellent food, or when I am eating dinner with people I enjoy, I prefer a quiet setting so that I can either enjoy the food and/or the people. I find the music and other noises to be distracting.

Update 22 March 2016 I decided to purchase these IKEA plastic utensils that are intended for children after seeing this photograph from one of the customers that showed that they were not much smaller than utensils for adults. They have turned out to be better than the utensils that I created myself, and stronger than the plastic utensils that are designed for camping. Some men might have such large hands that they are uncomfortably small, but they are fine for me. They don't have a soup spoon, and plastic knives have limited value, but their fork and spoon is excellent.

Here are some of the plastic utensils that I've made for myself. Plastic forks and spoons can be useful if designed with enough strength.

Whatever this black material is in the photo below - apparently some type of fiber reinforced plastic - it is very strong and useful for forks. This material can also make a knife that can cut through soft foods. Unfortunately, I had to make this fork from a flat piece of the plastic, and the flat shape is not quite appropriate for a fork.

Here is one of the large plastic spoons that I've modified for mixing ingredients in a bowl. It doesn't scratch the glass or porcelain bowls, and it's quieter to use. Is it possible to give a heavy plastic coating to a steel spoon or fork? If so, that would give us some forks and spoons with the strength of steel and the quiet, non-scratch qualities of plastic.