> but in each generation, people find it initially shocking to see so many people wearing what is marketed and made for sportswear for leisure, or even seeing it spill into the workplace. i think the article was focusing on leggings when they started creeping into non-sports-related settings.

A lot of modern casual and even business-casual fashion is (or was) sports wear.

Polo shirts? Explicitly designed for tennis—it's the reason the design exists. Pure sportswear.

Oxford-cloth button-downs? Sports wear. That's why it's got the buttons to keep the collar down, and why the cloth is so heavy-weight and rugged.

Rugby shirts? Jerseys? Of course.

Sneakers, of course. Also, many other shoe designs, from equestrian and hunting sports.

What's not sports wear is often former underwear. T-shirts and A-shirts (thought the latter remain very informal, at least) were/are underwear. Arguably leggings are underwear that (somehow—this trend remains baffling to me, but on the other hand, I mean, thank god for it, obviously) became sports wear and then became everyday casual wear.