In a liberalised economy, there is little regulation on forex reservation. The forex ends up in circulation among the citizens this leaves the governments unable to do any international transanction without the forex reserves.
The decision that follows is to devalue the currency so that the population would find it attractive to sell their forex. But what this decision neglects is the fact that for businesses that depend on imports, the cost of their imported goods gets higher. As a result of this, the prices of things gets high. and the rest of other things also gets high. Now of these changes, those dependent on salaries, suffer a lot as the salaries are the least considered in all these changes, for a rise in salary also raises the labour cost also requiring a rise in the price of the products.
The cost of living gets high. After devaluing, the exchange rate is left as is. That means that every year the currency has to be devalued to recover the forex earnings.
This is devaluing is necessarily a fix to the problem arisen due to liberalization of forex management. But it creates many other problems in the the money flow ecosystem.
What devaluation does is economically depress a region that uses the devalued currency. In the end the region's benefits from exports gets smaller and smaller and the loss from the imports gets bigger and bigger since the currency can only be devalued with relative to other currencies for the the government to get required benefit from the devaluation which is in fact: getting back the forex from circulation into the forex reserves.
The benefit from devaluation is smaller than the loss from it. Hence there is need to find other ways of regulating forex with the benefits of liberal economy but also to allow regulation of some economic activities.