I'm not really sure why the fact that you personally own something means it's not a fashion item.
Crocs are definitely in at the moment where I live, especially with teens and tweens.
Lucy and Yak are as much of a fad as, for example, Nike pros, they're just popular with a different demographic.
The fact that it's 'quirky' middle class women who like everyone to know how ethical they are who wear L&Y rather than youngsters doesn't make it less of a trend, it's just more accepted to mock teen fashion.