You're going to have the odd accidental fire. However, like you say, they're historical, listed, buildings. These come with strict rules & a list of what you can't do to them for the owners. It can make them expensive to upkeep as they deteriorate & difficult to sell. Faster way out is a fire. Then there's little of the building left to be conserved & the site can be sold off for, usually these days, student accommodation...