Back in '81, I had a 9 page presentation designed for display on computer monitors. It worked beautifully at our site.
However, when we went to the client, their connection was 300 baud.
There was nothing more agonizing than watching the cursor plod across the screen - row by row, character by character. :~ Thoughts of 'Will we be able to sell this to them?' coursed through the brain.
Fortunately, the client was very patient. We did sell it!
But I learned, that day, to always view things from the Client's point of view.

It's helped my code design and development to this day.