Because that's the way Anishinaabemowin is spelled using Latin characters.
Edit: typo
Ok, I'm being a bit pedantic, I admit it...............but .....I feel like it must be said...
Anishinaabemowin has no alphabet or written composition of its own.
It was an oral language, and it was largely translated by Frederic Baraga in the early to mid 19thC - he, a Slovenian Roman Catholic Priest.
So it is to Mr. Baraga who we owe an 'interpretation' of how to spell words from this language.
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It should be noted, In English we don't retain most original country or place names from foreign languages.
We say Germany, the Germans say 'Deutchland'.
We say Spain; the Spanish say 'Espana'
We say Italy, the Italians say 'Italia'
So there would nothing uniquely pejorative or insulting about making a pronunciation easier to the English ear.
This habit, by the way is not unique to the English...........
In a majority of European countries, Canada is spelled Kanada. As the C is not hard in many languages.
France, of course, spells the United States; Etas Unis, by literally translating the words, rather than assuming it is is a proper name.
Meanwhile......in Italy the City is Firenze; we call it Florence, and the Germans call it Florenz.
None of which is to waste time arguing the merits of the choice here, but merely to note, the spelling and pronunciation in most languages of most words from other languages is actually written and spelled by the receiving or translating party, not the originating one.