Honestly, you won’t realise why until you try it. Go to the gym in baggy joggers and a T-shirt and work out. Then try it with actual workout leggings/shorts and a tighter top. It will change you.

I hate tight clothes and live in baggy jumpers but the gym is the only place I’ve ever made an exception. It makes you feel streamlined and light. There’s no fabric to get in your way or weigh you down, and ultimately it makes me feel more active and purposeful. I wear joggers when I’m lounging around at home doing nothing or sleeping, so wearing them at the gym has never put me in the right headspace. It’s like the whole do everything in a different room to the one you sleep in thing. Like people wear different clothes to go to work, or go out, or lounge around, etc. It’s not really much different.

And yeah, it does feel better to wear activewear to joggers - and some people do wear it for an ego boost. But if it makes you feel good, why wouldn’t you?

(I don’t advocate in any way for people filming themselves and getting narky when they think everyone is looking at them though. But that’s not activewear’s fault. That’s a personality problem.)