Bhutan's approach to tourism is very deliberate, and it prioritizes sustainability and cultural preservation.1 This leads to certain regulations that can make it seem "difficult" to enter, compared to more conventional tourist destinations. Here's a breakdown of the key reasons:
"High Value, Low Impact" Tourism:

Bhutan's core tourism philosophy is to minimize the negative impacts of tourism on its environment and culture.2
This means they aim to attract fewer, higher-spending tourists, rather than mass tourism.3

Sustainable Development Fee (SDF):

The SDF is a daily fee that all tourists (except those from India) must pay.
This fee goes towards funding sustainable development projects, including environmental conservation, healthcare, and education.4
While this contributes positively to the country, it also adds to the overall cost of a trip.5

Controlled Tourism:

While changes are happening, Bhutan has traditionally managed tourism through licensed tour operators. This ensures that visitors have guides and that their itineraries adhere to the country's regulations.
This system helps to regulate the flow of tourists and protect cultural sites.

Focus on Cultural Preservation:

Bhutan places a strong emphasis on preserving its unique culture and traditions.6
The controlled tourism approach helps to prevent cultural dilution and ensures that visitors experience authentic Bhutanese culture.7

Infrastructure Limitations:

Bhutan's infrastructure, while improving, is still limited in some areas.
This can affect the number of tourists that the country can comfortably accommodate.
For example, Paro International Airport has unique challenges, and the countries road infrastructure is still developing.8

Essentially, Bhutan's tourism policy is designed to balance economic benefits with environmental and cultural preservation.9 While this can create perceived "difficulties" for tourists, it also contributes to the country's unique and pristine appeal.