I was going to say, it is one less thing on the checklist of things to do before the next guest arrives. They probably weighed that up against the number of people who genuinely read them and said "screw it, if they want one they can ask for it". I'd say most people who insist on reading the bible anywhere they go will have their own personal copy with them.
indeed especially as most people who are devout enough to read each night etc will have one particular to their sect/choosing.
people forget there are many different bibles.