I’ve had a number of iPhones and while I’ve cracked a screen or two, I’ve never had issues with scratching, at least not like this. I’ve had the iPhone 8 for a couple months and it’s very noticible and becoming problematic. Why is the “the most durable glass ever” so susceptible to normal wear?
While it's certainly scratch resistant for glass, it's not scratch proof. The worst conditions seem to be where there's a lot of sand.
Material strength/toughness isn't an easy thing. There's always some sort of compromise between scratch resistance (hardness) and durability (toughness). In general synthetic sapphire (used on iPhone camera lenses and over the home button) is the most scratch resistant materials that's relatively inexpensive to produce. But it will shatter easily.