I want to know what was running through the mind of the first guy who thought up mummies. Some guy just came along and said "You know what we need? Dead bodies to last longer! C’mon, who’s with me?”
We might need them to still look good in case they DO reanimate, or maybe Picture Day in the afterlife?
I wonder how much time it took from the proof of concept to the first successful mummification? Trial and error and such. And how did they quantify a success? Dig them up every year to check?
Also, people were very influenced by religion and superstition. They may have interpreted mummified bodies as some connection to gods/goddesses. They in turn took up mummification based on this understanding, not because it seemed cool.