Well, in the case of tumblr, most users are not technically proficient enough to know what's going on there. Plus, they certainly don't care about tumblr's costs, unless their pictures load noticeably slowly. And even then... well, let's just say most tumblrs are not exactly carefully-maintained gardens. So tumblr is likely serving tons of wasted data, slower than necessary, harming most of their user's experiences by preserving that data. Consider mobile users with limited data plans - they likely don't feel much sympathy with your argument.
Compromise: tumblr receives the image, compresses it, and shows the result to the user saying "how does it look?", as well as a disclosure triangle to show the list of optimizations it made, noting that if the picture looks wrong, to click it. When that disclosure triangle opens, it also offers a button saying something to the effect of "use what I uploaded, damn it!"
The vast majority who don't care click right through, those who do have a simple interface to see exactly what's going on with their image, and X thousands of pages can load quicker and save millions of people's bandwidth (and tumblr a bunch of money). Mobile users don't waste money on useless data and their images load much faster.
Compromise: tumblr receives the image, compresses it, and shows the result to the user saying "how does it look?", as well as a disclosure triangle to show the list of optimizations it made, noting that if the picture looks wrong, to click it. When that disclosure triangle opens, it also offers a button saying something to the effect of "use what I uploaded, damn it!"
The vast majority who don't care click right through, those who do have a simple interface to see exactly what's going on with their image, and X thousands of pages can load quicker and save millions of people's bandwidth (and tumblr a bunch of money). Mobile users don't waste money on useless data and their images load much faster.