Because we have the whole notion that even acknowledging the existence of intelligent design theories is somehow unscientific. In other words, it's only "real science" if it agrees with a certain viewpoint.
It's intellectually dishonest, smacks of fear and quite frankly, intolerance.
It amazes me that people think having a science teacher simply say "some people believe that a higher power exists, and that higher power created everything" is such a big deal to people.
Not everyone interprets the "evidence" the same way you guys do. But you're not willing to accept the idea that an alternate interpretation is even possible.
That's just intellectual cowardice.
At this point I do not think you have any idea what you are talking about.
There are very few biologists that do not acknowledge that there are people who believe in intelligent design... but why the heck would you teach philosophy in a science class? And how do you decide which philsophy to teach?
Why is YOUR creation story better than the Indian creation story? Why is it better than the Japanese? Or the Hopi? Or the ...
When I was introduced to a bit of depth on evolution in high school, it was definitely preceded with, "There are many religious stories about how life came into being. We aren't going to discuss those, because this is a science class. We're going to be learning about observed explanations for life and how it has evolved on this planet."
The problem is that people that advocate "intelligent design" aren't content with things like that. They want to "teach the controversy" or some bullshit. There is no controversy here. There is philosophy, and there is science.