I wear jeans and a tshirt to work most days. My job itself [caregiving for the elderly, same duties as a CNA] is serious, but the setting is casual because I take care of her in her own home. I don't dress up at all obviously because occasional messes of whatever sort are an occupational hazard, and no one even sees what I'm wearing except her, but she's blind and wouldn't care what I was wearing anyway. I could wear scrubs to work and it would suit the job, but I haven't felt like investing in any in the two years I've been doing this. I just wear normal casual clothes.
I work with psycho-sexual people. Or psychopaths. We aren't allowed to wear anything that can cause harm or be used to choke someone by having it tossed down their throats. No jeans for us. Not even buttons. Tee shirts and leggings or skirts not zippers or buttons. No shoe laces and no hair elastics.
Right now while I'm still in college I don't have a serious job so yes, it's actually kinda required. I work as a landscape assistant for a family friend so the sturdy materiel jeans are made from is perfect for my job. I don't mind unless it's a super hot day. Then I hate them because I'm sweating like crazy and they get all soggy.