Earlier quoted context omitted.
Well that's your answer to your question. You forgot to optimize the images, because with your test environment, you don't notice it. If you were testing over a dial-up connection, you would notice it. Same with app writers. They forgot to optimize their app because they're testing it on the latest and greatest phones on their home network (or a corporate network which is blazing fast). If they tested on a low-end ph…
I used to work at a shop that ran a 1.5 mbps dsl line, and a ~5 year old, cheap, slow computer. If their code worked on that, it would work on any of our customer's machines. I wish devs would still test like that. Sure, your app works fine in downtown SF on the newest phone, but try using it in Nowherseville, TN, on a phone that is more than a couple years old. I bet a lot of user frustration comes from dealing with…
Granting that you heavily imply a 4G connection, the choice of "Nowherseville, TN" is extremely interesting: Chattanooga, TN — which as a Tennessean I feel is essentially "Nowheresville" to most non-Tennesseans — has Internet service multiple orders of magnitude better than most of the Bay Area[1]…
[1]: https://www.washingtonpost.com/news/the-switch/wp/2013/09/17...