[nogridbag]

I've always assumed the reason is because only a tiny sliver of Christians have actually read the whole bible - so they probably have no idea what it says. A quick google search seems to confirm my assumption [1].

[1] http://www.christianity.com/1270946/

[spacehome]

I've always assumed it's because if you read it it's filled with some awesome love/acceptance/transcendence stuff and some really terrible bronze age horrors. It would be too terrible to actually take it at face value.