matsukov - that's also how I understand it is in the UK. The Charity Commission can use it's remit as long as WTBTS are a charity. But if they lose that status then WTBTS can do whatever it wants untrammeled, so better to keep them a charity.
Losing charity status also means the accounts would no longer be public, which gives us a bit of insight for the moment on their financial health somewhat, and how much they are siphoning to US head office.
Having publicly appointed trustees might have quite an impact on them though. Could they stop siphoning funds and also spending on building projects until there is suitable reform?