Technically, the term "sneaker" comes from how quiet the rubber soles are—you can "sneak" around in ‘em. So yeah, rubber soles are a must.
But imo, it’s also about culture. Like, nobody calls Crocs sneakers, even though they’re comfy and rubber.
But imo, it’s also about culture. Like, nobody calls Crocs sneakers, even though they’re comfy and rubber.