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.
Rebuild by donations is asking for the project to delay for decades. Look at La Sagrada Familia for enough evidence of how long it takes to construct a culturally significant cathedral using donations and no state support or private investment.
Maybe cathedrals are meant to take decades? Time spent that takes longer than a lifetime makes the building non-disposable, and it makes its builders understand they are working on something bigger than themselves. Consider that some took centuries to finish (looking at you, Cologne).
The state handing money means that some parts of the state ruling infrastructure consider the cathedral building to benefit a small part of society - the part that keeps the "representatives" in power. Especially in Europe, where church power has waned in the last decades, I don't think it's appropriate for a government that is supposed to also represent Muslims or Atheists or Buddhists to spend significant resources on the building of a cathedral.
That being said: as a non-christian German I gave a - to me significant - amount of money to the Notre Dame rebuild. I like the idea of helping build a piece of art that will survive me.
Yet here we see there really must be a need for insurance. If the building were insured, there wouldn't be a need for donations from around the globe to support its reconstruction. It would just be done out of policy. If the state was able to do this on their own and actually earmarked money in the budget to actually self insure this building, there wouldn't be a need for donations from around the globe. The state can't pay for it, which is why donations are required.
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.
[1] https://www.frauenkirche-dresden.de/reconstruction