It's so ubiquitous as to barely be a trend anymore. To put things into perspective Yoko Devereaux had them in the mid 2000s, and there were some Margiela versions before that, though the style of garment was not well known. I think that "sweatshirt" jerseys may cease to exist, but we are going to have sportcoat-cardigans for at least a while longer. There were a lot of different takes on them at Pitti Uomo.. Basically, they are easy for guys to wear with jeans (a lot easier than a more structured, woven, blazer), and a relatively inexpensive cut-sew. so there is incentive for designers to make them.
What's wrong with them? I have a cotton thing from Club Monaco that was $30 that's somewhere between a blazer and a cardigan that I wear all the time. It's really easy to wear & looks good, which honestly is what I look for in a garment. I have trouble pulling off a real blazer in a lot of settings where I can wear this.
Meh, who cares what others do? Some of my favorite people just wear gym clothes 24/7