For those wondering, why the "low" age of consent:
Most cultures in the planet, had age of consent around that time, for example in Athenian Greece people made a point to marry girls at that age (something Spartans didn't liked, because pregnancies were riskier).
In Brazil, when the countries all started to bump age of consent to 18 or 21, and introduce strong child porn laws, went along, and put age of consent to 18, and child porn laws the mininum age is 18 too...
This created problems, in many parts of Brazil, people still married at 14, sometimes with both being "underage" (14 year old bride with a 16 year old groom for example), and in the "westernized" parts of Brazil, like São Paulo and Rio, it is normal to lose virginity (usually against parents wishes) in ages between 13 and 17
Thus, age of consent law at 18 was obviously unrealistic, 15 year olds were fucking (and marring in some cultures) like rabbits, and thus you suddenly made a huge swath of the population criminals for no good reason, just to please other countries.
So, a compromise was made:
Age of consent is 14, but if the minor (someone between 14 and 18) complains to the police about being raped, or "seduced", you get harsher punishment (ie: you are treated as pedophile)
Age of consent for sex photos is still 18 (ie: even if you legally marry a 17 year old bride, if you take a picture of her, and someone finds it in your stuff, you get arrested for possession of child porn)
This way Brazil could make other countries happy, while not making most of the teenagers criminals for no reason. (also, "Romeo and Juliet" laws wouldn't work, in Brazil native american communities, or places more isolated, girls frequently marry a guy much older in hopes of having a better life, as those guys usually are already educated and have jobs, and thus can afford taking care of the house financially while the girls finish their education, in contrast to their parents, that might have too many children to support, and can't do it).
EDIT: tl;dr: age of consent law was first 18, it obviously clashed with local culture, thus it was lowered to 14 that makes more sense.