I would guess it's down to history? I was working on a group of buildings and this
was what I was faced with. I was just too big to reach them could only take a photo and I had to add a RCD elsewhere with a new earth rod.
It does not really matter why but where one can't access equipment one can't service it, and getting the DNO to visit at the same time as an electrician so their equipment and your equipment can be up graded at the same time can be hard.
Clearly the power to the other flats would also need turning off so likely it would mean each tenant plus an electrician plus the DNO all arriving at the same time.
You don't have RCD protection and clearly it would be nice to add that but only you can decide if it's worth the cost to upgrade. At the moment from what I can see replacing the consumer unit would be easy as there is a big main switch to turn it off. Although not sure what other tenants would say! However if they all rang the DNO complaining of no power I suppose they would have to do something about moving it all.
The picture I have shown also feeds three buildings however all used by the same man. But clearly in the future that may not be the case. In fact he wants to demolish the building with the meter in and the only reason it has not been demolished is the electric supply.
What we need is a leprechaun electrician who can get in the space.