The previous owners were using it as a single family home (according to Wikipedia). Make of that what you will. It's definitely a bigger 'waste' of resources than using it for conferences.
No-one cares about the waste of resources though. A castle is a symbol of power. It's the combination of lots of big, bold ideas, lots of public speaking, giving money out, THEN buying a castle. People begin to worry that these people want to rule them.
