ironically, they have laws that demand free SMS on most plans. i think only a few categories of pre-paid plans do not. Though that is changing. Couple years ago there were laws that set maximum prices on internet and sms for pre-paid plans (R$0.5 a day!), but the telcos already lobbied the downfall of those for this year.
brazil has a huge mentality of "belonging". Supermaket chains that market to upper-middle class (think whole foods) charge 4-10x more for the same product (R$20 instead of R$2.50 for bottled water, same brand). and they are usually just a block from a regular market. yet, you see lines just because people want to belong by purchasing there.
WhatsApp was huge for people that needed to talk to folks overseas in brazil, and close to half the upper class and a large portion of the middle class in brazil sends their kids to study abroad. So flaunting WhatsApp instead of SMS is also a way to show off.
I don't know where the parent lives in Brazil, but the supermarket chain comment definitely has not been my experience in upper-middle class Rio de Janeiro neighborhoods.
People use Whatsapp instead of SMS because it simply is a better user experience, specially for sending media and group chat, not for showing off, or keeping in touch with relatives abroad. Phone companies began offering "free whatsapp" even in pre-paid plans because it because it became very popular, as a way to attract costumers, not the other way around.
Even more bizarre, because WhatsApp use phone numbers as ID, I see people exchanging phone numbers willy nilly!
For example a married woman that wanted to cheat on her husband that is not having relations with her, sent me a message with her phone number asking me to talk to her on WhatsApp (but at least remembered to ask me to not call her...).
I am not into that stuff, still, that was only ONE example, in that day, I joined a evangelical christian chat when I was bored, and there was there lots of old guys clearly looking for sex (they had nicknames like "big cock 57" while moderators were out), and I saw a girls younger than 16 posting in the open chat their "watsapp" numbers wanting to chat, probably without realizing this were their personal phone numbers.
Also I've seen people going to great lenghs to stay anonymous online and then exchanging whatsapp number without realizing you can use this to track their real name down (unless the person was conscious enough to create a fake ID when buying the phone number, something I doubt that most people do).
