Because during the middle ages, when some English monks started to standardize spelling rules, they decided that any word ending in a "GE" sound would end in a G-E, because all English words ending that way were loanwords from French-Latin. But some of these loanwords (such as "bage") had Anglophone pronunciations, while others (such as "espionage") were still Francophone. " To avoid confusion, the monks decided the Anglophone form would end in "D-G-E" (hence "badge" instead of "bage") while words of the Francophone kind would retain the "(vowel)-G-E" ending. This patter persists today, which is why it's spelled "fridge" and not "frige," as the latter would have rhymed with "liege." However, this patter does not apply to certain words (like "manage") because at the time when the monks were standardizing English spelling, "manage" still rhymed with "espionage."
Sincerely yours,
A fellow meme farmer