I agree with you but we are in the minority. For some reason NFPA and the manufacturers have decided a detector in an unservicable location is better than one you can get at because of a minor increase in performance.
BTW this is really dependant on the manufacturer's installation instructions. NFPA72 only gives guidelines and defers to the instructions for definitive guidance.
The first manufacturer who labels his detector for an accessible area will make a fortune.
You also have to note the location of paddle fans. My wife got away with not putting detectors in the coffered ceiling trays because there was a fan in there.
Personally I think it borders on criminal to put a detector with user replaceble batteries where the user can't get to them. You know the first time he pays $100 or more for the service call to get someone up there they will tell the service tech to pull it down and throw it away. (I have seen it happen)
My wife was carrying the "duty pager" for her company for 2 weeks. She got 2 calls. One to disconnect a pool door alarm and one to move/remove a beeping smoke detector 27 feet from the floor. She could only tell them she was not allowed to do it. Call someone else.
