People spending way more than they need to at laundromats
Under-filling washing machines doesn't get your clothes any cleaner than stuffing them full.
Under-filling dryers doesn't make your clothes dry faster by a big enough margin to justify using more than one dryer.
I worked in a laundromat on the weekends when I was in high school (early 1990s) and I saw people spending double, triple, quadruple, etc., what they needed to spend, all the time, especially with dryers. I was in a laundromat today for the first time in years and nothing has changed.
There's a minimum amount of time that it's going to take to dry clothes, even if you're only drying one pair of jeans and nothing else, and that's about 40 minutes. There's also a maximum amount of time that it's going to take to dry clothes, even if the dryer is full, and that's about 50 minutes. That means it's impossible to save money by spreading a load of clothes out among multiple dryers when they could have fit into one dryer. At best you'll save 10 minutes and inevitably pay a lot more (close to double the cost for two dryers, close to triple the cost for 3 dryers, and so on).
There were some people who would spread a big load of clothes over six dryers, spending $9 instead of the $1.75 it would have cost had they used one dryer, and they'd do that every week.
I guess they think that their "wisdom", which may be somewhat valid for pathetic home-use washers and dryers, applies to big commercial coin-op machines as well. It doesn't.