It always surprises me how much this topic comes up... and I think it's normally people who view it from the "outside", like grandparent, upcoming parents, etc. Since I have kids in the thick of this situation (age 4 & 8), let me shed some light.
Most sports for ages 4-7, are the everybody plays, everybody wins, sometimes the keep score, sometimes they don't. The leagues are basically for teaching little kids the games (baseball, football, soccer, etc.), having fun, getting exercise. Once kids hit about age 7 (first grade) and up, for most sports there becomes two different paths. The competitive route, and the just for fun route. There's travel baseball where kids compete in tournaments, there's tackle football and not flag. The noncompetitive path still does keep score, and has winners/losers... but is the type of league where everyone still gets a trophy at the end of the year. I think this is great for kids who aren't serious sports players to have fun, get exercise, learn the game, etc.
The competitive path is insane. I believe kids are constantly getting better and more amazing even younger all the time. Think of how many 18 year olds go straight to the NBA now, how many rookie NFL players actually start now, how baseball is drafting younger and younger. These kids are so amazing and so good, they practice all the time, parents spend THOUSANDS of dollars every year for private coaches, lessons, equipment... there's no place for kids who just play for fun and aren't that great (hence why the other leagues started springing up). These are the parents that are also insane. You scream, yell, and get into it because this is something your kid is so dedicated to. I think sometimes parents look harder/worse than they actually are because they know their kids want this and they're just pushing them through a rough spot (although I am sure, just like anything else some do cross a line).
We have experience with both tiers of sports. My son plays baseball for fun, and does football competitively. He's been invited to be on the travel baseball team, but we don't have the money or time to commit to it, nor does my son have the passion for it. It's fun, he plays with friends, he has great days where he hits homeruns and bad days where he strikes out. They win/lose, had a mini tournament against some other "fun" teams and even though they were seeded second, lost right away. It is what it is and likes doing it with his friends in the spring.
My son plays football competitively, and LIVES for it. He hurries through his homework at night so he can sit at the table and write his own football plays, he plays madden constantly when he can't find anyone to throw a real ball with him, he RUNS constantly to train, he works out until we have to tell him to stop and rest his muscles. Boy is a beast and loves every minute of it. He's a running back and scored 17 touchdowns last season, he was second in the league in touchdowns to only one kid.... the son of a NFL running back who has a Super Bowl ring.
So basically you need to find the right league for what you and your child want to get out of the sport. It's not "there's no winners and losers anymore! everything is too PC!" or is it "parents are too hard on their kids, they should play for fun!" Just do your research, and talk to other parents, and find the right type of team for your kids.