Maybe because originally "America, Land of the Freeloaders, Home of the Timid" or "In Quakers We Trust" just didn't make the cut..
Or because the majority have decided that the words "In God We Trust" have the same import to Americans as "..Mom and Apple Pie", and as such, have become intwined as part of the American Identity.
Why would I consent to having the words of my childhood pledge to my nation expunged and removed from the public psyhe on basis of a wailing from a voicefrous minority?
The Supreme Court in essence told the ACLU "get lost" on this subject.
If you think it's hateful and offensive, and just can't stand it... well gee; too freakin bad. So Move.