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English is a language in which you write quite a few letters that you do not pronounce, or you write letters in one order and pronounce it in another.
For example, centre. It is pronounced /ˈsɛn.tə(r)/, so you say e before r, but you write it the other way around. Or Google: /ˈɡuːɡəl/; you say e before l, and then you write it the other way around.
One example of a letter written but not spoken would be practically. You say practic-ly.
There are quite a few examples of that. But I don't see why those things seem to develop.
I am a German, and (most of the time, with a few exceptions) we speak all the letters written (or at least significantly change the pronunciation of the other letters at some points).