I think they sort of do, it’s a form of signaling.

It’s the same game we play verbally with slang. Slang word gets made up, people use it so others know they’re in the group that uses the slang, usage spreads until it’s no longer a group indicator. You see it all the time as an age grouping. You can almost guess someone’s age by the slang they use for “good” (cool, lit, bussin, etc).

This is the same. Startups invent a new UI style to separate themselves from the incumbents, incumbents eventually copy the style, cycle repeats.