And a lot of scientifically literate believers in God also don't believe the Earth is 5,000 or so years old and so on. But just as ID gets used by biblical literalists as proof of their particular God, there are hard-core atheists who use evolution to undermine belief in God. This forum attracts a lot of Fundamentalists so it seems like there are a lot of them. Go to another forum that is dominated by atheist activists and you'll get a very different impression.
In the minds of many people, evolution is seen as incompatable with a belief in God. Teaching ID raises the possibility of guided evolution and makes it clear that religion can have a place alongside science. That's really not all that different from what my friend says he was taught in his Catholic school. As an added bonus, it encourages people to look more deeply into how biological systems work and change over time.
In many ways, it's a compromise. And unless you think a winner-take-all knock-down drag-out battle over teaching evolution or biblical creation in schools is a good thing, it makes a lot of sense to make a relatively harmless nod toward creationism. Remember, it's always possible that you could loose the "winner-take-all knock-down drag-out battle" and then you'll have a lot more to complain about.
Camel's noses and tents come to mind.