People frequently get burned. There are often projectiles that go into the eye. But that doesn't mean they're safe. Even a sparkler, in the hands of someone who's been drinking, or the hands of a child, can be dangerous. Sparklers burn at about 1800 degrees Fahrenheit, easily enough to start someone's clothes on fire.
Children think they're great to look at and they try to catch the sparkles with their hands.
And we've seen people who've gotten burned. Fireworks cause about 30-thousand fires every year.