They made them in plastic later on. We had them in the military. Took 2 D cell batteries. Provided a couple of hours of dim light. Heavy, clunky, but it was what was available. The idea that you could have used them to hike long distance on an unknown trail would have been laughable. You used them to find things in the tent and light your way to the latrine.
The revolution happened when light emitting diodes that provided white light became available. Flashlights using the LED technology came into the market around the early 2000s. Then they proliferated. Everything from tiny keychain LEDs to flashlights similar in size to the one above, but putting out thousands of lumens. That set the stage for this:
I was solo hiking, which creates the logistical problem of getting back to my truck on the day I come off the trail. I had called a man that makes side money providing shuttles along the Appalachian Trail in the area from Connecticut to Vermont. He said he could pick me up where the trail crosses the highway north of Bennington, Vt., but he would have to meet me no later than 9:30 AM. The shelter was four miles from the road. In that terrain with a pack, I'm not averaging much over a mile to a mile and a half an hour.
I woke up at 5AM. It was full dark. As I dressed and got ready, I was using the headlamp. I used it while I packed, while I made breakfast, and most importantly, at 6:10 AM, I put on my pack and hiked off onto an unknown trail, trusting the headlamp to light the way. I hiked with the headlamp until after 7, when it got light enough to see clearly. I came down the long descent to the highway about ten minutes after nine and met my ride.
It would not have been possible to make that choice without that LED headlamp.
There are lots of designs, some brighter, lighter, more efficient, and more expensive. Mine is middle of the road and I bought it in a local outfitter. Even the cheapest of them, available in a big box store, are like science fiction compared to what was available less than 20 years ago.