Because everybody knows GIF means Giraffe Interchange Format!
It was invented by rangers in the Serengeti for keeping track of Giraffes changing between areas. They made graphics illustrating those movements, and the format they used became knows as GIF. That's the secret history of the image format.
The situation is different. The first letter in "photo" is not the "p" but the "ph". They are one. The "h" is a modifier. In "graphics" there is no modifier on the "g".
TL;DR H as modifier was introduced when translating Greek and they were lacking appropriate letters in Latin.
> I'm a phoneticist and a general linguist and "PH" and "F" are, indeed, pronounced the same, and are both represented by /f/ in the International Phonetic Alphabet. Greek Phi was once pronounced as a hard "P" in Ancient Greek. So, Latin inscriptions wrote it as "PH" to show that it's a P sound, but with more air with H. As Greek changed, so did the Greek based English words. In Modern Greek, Phi is pronounced as "F", and no longer like "PH"/a hard P.
..and I forgot: That means that it should have been J-Ph-EG and not JPEG. They created a completely different first letter by ignoring that "ph" is one letter. The J-PEG pronunciation was obtained by using destructive force.
It was invented by rangers in the Serengeti for keeping track of Giraffes changing between areas. They made graphics illustrating those movements, and the format they used became knows as GIF. That's the secret history of the image format.