If you say that Brazilian schools teach an "artificial" language when compared to that one spoken everyday on streets, I agree with you. But the statement implying that "Simple Past" and "Past Participle" are useless stuff is just bizarre and to hear that from a guy living in the USA is even more bizarre.
You can hear "Past Participle" in films, songs, speeches, everywhere. And that happens simply because "Past Participle" is the way you say something that started in the past is still happening. It´s a matter of vital information about what you are willing to say. If you say "I´ve lost my keys" you are not saying "I lost my keys", they´re two completely different contexts.
If you are in your house with your american girlfriend and you say "I´ve lost my keys", be sure that she´ll be glad to help you saying: "I can help you look for them if you wish". But if you say "I lost my keys" (meaning "I´ve lost"), all you will hear will be: "Really? Where were they?", because the Simple Past just told her that you have your keys again. Yes, just by using a specific verbal tense.