It's A Moot Point

I keep hearing people say "mute" point, pronounced like the word meaning inaudible, when they mean to say "moot", a word meaning irrelevant. Today I saw it in written form. The person (a lawyer) in question clearly meant "moot", given the context of the sentence, but typed "mute". Why is this? These words don't sound alike when pronounced properly, and their meanings aren't similar, yet it's a fairly commonplace mistake. Further confusing the issue, no one ever makes the opposite mistake, saying "moot" when they mean "mute". When did they start getting confused, and why?