Reason is that it is also an interface for SMS, and SMS in Brazil is obscenely crazy expensive, some operators might charge 1 BRL per message or stuff like that (for context: 1 BRL is the price of a cup of coffee or of a bottle of water), using iMessage and having it to switch to SMS without you noticing can rack bills that are easily bigger than your wages.
Reason is that it is also an interface for SMS, and SMS in Brazil is obscenely crazy expensive, some operators might charge 1 BRL per message or stuff like that (for context: 1 BRL is the price of a cup of coffee or of a bottle of water), using iMessage and having it to switch to SMS without you noticing can rack bills that are easily bigger than your wages.