lz clarify my doubts on tractor?????

Plz clarify my doubts on tractor?????
1)why most of the tractors are made with no covering for users?????i found most of the users want some covering from rain. i mean tractors with cabin will be better design

2)only driver is allowed to sit on tractor. then hw can some manufacturers design tractor with seating on top of both wheel arc

3) why there is not much improvement in Indian tractor design?? is it bcoz the presnt design suits best for indian condition
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