Re^6: My favorite silent English letter is:

[mertserger]

I am not sure you can ask "why" when it comes to features of natural languages. Unlike Klingon or Sindarin, they aren't designed; they evolved. The reasons for the path the evolution took (if there were any) are lost in the mists of time.

[Anonymous Monk]

The reasons for the path the evolution took (if there were any) are lost in the mists of time.

But you can safely assume, that humans being humans, wanted to be proprietary and sound cool, and then other humans tried to emulate them as best they could.

[mertserger]

Yes English-English pronuciation often contains minefields even for English people as some words are (or were) used as class-markers or signs of greater/lesser education. It has been said that no Englishman can open his mouth and speak without another despising him.