The envelope is a great invention, just like a spoon. One day you can develop more advanced social media than Facebook. Or you could do a better search engine than Google. But can you make a better spoon than a spoon?
The spoon was invented thousands of years ago. And it's still in use.
The envelope is the same. Once developed and used without the need for an add. What's missing. What more. Perfect and simple design.
Colored, floral or scented envelopes were made, but they did not contribute to the function.
The envelope is still the same as the envelopes developed centuries ago.
I mentioned above a6 envelope size.
If you want to learn bigger or smaller envelopes, here are other options: