Why would they turn away good money coming into their economy?
The majority are Hindu. They see Christianity as invasive and maybe divisive. They're probably ok with it growing organically, but don't want outside influence causing an abnormal growth. They may also be aware of the cult tactics and are looking to protect their citizens. Also, other than building, what would the WT actually contribute to the economy? Members are sending their money back to the org so it would end up as a net loss.