The Permanent Settlement was rarely extended to other regions because

The Permanent Settlement was rarely extended to other regions because :

increase in agricultural prices after 1810 increased the value of the harvest, while the Permanent Settlement disallowed an increase in the State’s share
the economic theories of Ricardo influenced the policy makers
the State found it expedient to settle directly with the ryot
all of the above
This question was previously asked in
UPSC CAPF – 2014
All the provided statements are valid reasons why the Permanent Settlement was not widely extended to other regions of British India after its implementation in Bengal, Bihar, and Orissa. The fixed revenue demand (Statement A) became disadvantageous for the state when agricultural prices and land value increased. The evolving economic theories, particularly those influenced by Ricardo (Statement B), suggested that the state should capture the increase in land value. Consequently, the British administration found it more financially beneficial and expedient to adopt alternative land revenue systems like the Ryotwari and Mahalwari systems in other territories, which allowed for periodic revisions of revenue settlement directly with the cultivators or village communities (Statement C).
The failure to extend the Permanent Settlement was primarily due to the financial loss incurred by the state from fixing revenue permanently in the face of rising agricultural prices and the influence of new economic theories advocating for the state to share in increased land value.
The Permanent Settlement created a class of loyal zamindars but deprived the state of a share in the increasing wealth generated from agriculture. The Ryotwari and Mahalwari systems, implemented in large parts of South and North India respectively, allowed the state to periodically reassess land revenue, ensuring that it could benefit from increases in agricultural productivity and prices.