Firstly, it's incredibly expensive. There's no regulation on the price you can charge for heat, and there's no competition for supply like gas and electric. So the apartment freehold owners charge eye watering fees for it. I could save probably 50-75% a month even paying for the cost on a new boiler, plus a service package.
Secondly, there are a lot of outages. Much more than I've ever experienced with standard boilers.
The outages are quite literally out of your control, unlike a gas/electric boiler where you can get someone to fix it out of hours. One particularly bad outage was nearly 48 hours in winter over a weekend, caused by incompetent building management and a seeming inability to get highly specialised parts from Germany to the UK to fix it on a weekend.
I've obviously had normal boilers break down but usually they can be fixed in a couple of hours, at least temporarily enough to get a proper fix sorted.
UK housing stock is in desperate need of upgrades, most houses are literally bleeding money through the walls because of poor insulation, and because heatpumps are much more efficient that boilers.
Consider that they are more economical when supplying several houses, pay for themselves over time and that interest rates are zero. It becomes obvious that we need a large-scale program of energy efficiency upgrades, it would create jobs during a recession and help address climate change.