"Same reasons that pertain to the Easter Bunny: there's no physical evidence that such a designer exists."
It appears that this is the crux of the matter. Scientists claim that no physical evidence that exists that can support the claim that a Creator exists. Creationists and IDers use the argument that the orderliness and complexity of the PHYSICAL universe IS evidence. Some scientists don't accept that as valid evidence so in their minds, no evidence has been presented.
That’s not evidence. It’s just restating the nature of the "phenomena", and then taking a wild faith based leap that God designed it (without evidence).
I support your faith, but not your desire to teach it to my kids in public school as a science. Keep it in social studies.
Evolution on the other hand is a significantly supported and pear reviewed body of theories and facts that deserves recognition as a scientific theory supported by evidence.