A cathedral is - among other things - a memorial to its builders. Changing the building is removing that function. Also, sprinklers may destroy more than they protect.
> The state owns all the cathedrals but doesn't insure them, so restoration currently has been reliant on donors,
This may be just me, but I find a rebuild-by-donations societally and spiritually a lot more meaningful than just some insurer and/or state handing over money. See also: Dresdner Frauenkirche [1]. It shows that society itself cares about the building, its history and cultural importance and spirituality.