Pet Peeve: Why do companies still send me my password through email?

Let’s face it; we all reuse the same password for login accounts all over the Internet. At best, some of us create a few passwords through which we rotate. So why is it that some companies still insist on sending me my password via email right after I create my online account? The reason I have a password in the first place is so that it doesn't flow back and forth openly in cyberspace only to reside peacefully on multiple mail servers.