It’s because English stole all its words from French. The pronunciation does not matter. As you say, half of the Es we don’t even pronounce. And half of the rest we mispronounce because of the Great Vowel Shift.

Is e the most common letter?

E is everywhere. In an analysis of all 240,000 entries in the Concise Oxford English Dictionary, OED editors found that the letter E appears in approximately 11% of all words in the common English vocabulary, about 6,000 more words than the runner-up letter, A.

What is the most common starting letter?

Wolfram Language™
Take the first letter of each word. firstchars = StringTake[words, 1];Visualize their relative predominance by generating a WordCloud. Compute the relative predominance of all the letters in all words by using LetterCounts. Now the most frequent letters are the vowels e, i, a.

THE MOST COMMON VOWEL IS SCHWA.

The most common vowel sound in English doesn’t even have its own letter in the alphabet. It does have a symbol, though, and it looks like this: ǝ.