All our Coach factories, and locomotive works are independent organizations. They are not obliged to supply rolling stock only for Indian railways. They just have to meet the demand from all of their customers, thats all.
This production is independent of the production they do for IR. It does not affect the coach throughput for IR in anyway. And these orders from other countries are usually one time orders and in small numbers. There are not continuous orders like the one for IR.
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more... Neglect from officials is more the reason for the accidents than lack of LHB coaches ( Just having CBC ICF coaches can reduce the fatalities to the same level as LHB in most minor derailments).