A dirty float is always what you will find on an economy that does not have good organisation because anyone wants to do what they like, it is important the best interests of the people for the government to step in and stabilise the exchange rate at such a time because when left without being checked, there are many private individuals that would take advantage of the negative situation unduly, this can have dire negative consequences for the citizens at large, fortunately this measure usually works because as the government intervene in the exchange rate, the people that are into this bad practice will retrace their steps if they don't want to lose all their money.

In a clean float, the government has little or nothing with intervention of what goes on in the country, this is why sometimes this can backfire.