The reason there's no photography permitted in the first item:
"In the past St Paul's has, as an experiment, relaxed the photography rule. However, the combination of camera flashes and groups queuing up to pose for photographs under the dome led to the conclusion that allowing photography would greatly detract from the spiritual life of the Cathedral."
There are also plenty of examples where commercial use isn't the issue, like with the trademarks, where things like "tarnishment" can come into play.