I've seen them once in my life, in Smoky Mountains, about 10 years ago. It was pretty much spiritual experience. The darkness came alive. I cried when I saw their luciferase smeared over windshield and glowing long after the creature was dead. I knew lots of lore about them, saw them in mass culture - never realizing I never saw one myself, even though I take care to notice all living things around, from bacteria and yeast to mycchorizal networks.
I live in Europe.
I do not have a lawn, I have several ha of forest and grassland. I have about 25 nest boxes for wild birds, occupied 2/3 (last year I had a huge owl living in one!) and countless other nests, several snakes, snails and frogs, lynx and I see bear tracks and scats now and then. I keep bees and allow wasps to build wherever they like, there are lots of bumblebees everywhere and birds sure have something to eat. I mulch a lot and keep loads of rotting leaves. I mow with scythe when I absolutely have to clear small area. I know there are fireflies in Finland.
Never saw a single blink.