Well, I'm stumped then. 
Maybe it's because we get our things second hand and/or I wash fabrics before sewing to make sure they don't shrink after sewing. OR it could be because we haven't managed to produce any children with hips
.
We get most of our clothes second hand as well. They will still shrink if the water is hot enough.
I know what you mean about boys with no hips, when my oldest DS was younger his jeans could have easily slid right off of him

because he had a flat tush & small (even for a boy) hips. Thankfully when he went through puberty he filled out & now his pants don't fall off.

Sure makes buying pants for him easier.
Back to the subject, I just thought of something else that would probably work. Years ago they did a study where for 6 months the cleaning solution used in a hospital for moping the floors, etc was 1/2 cup of borax to each gallon of hot water. It killed the bacteria, etc & all the testing showed that it was a good disinfectant & the tests that hospitals run to check for bacteria counts, etc all came back good. Borax is a good antifungal as well. You could soak the clothes in a bucket of warm water with say 3/4 of a cup (more borax since the water isn't as hot) to each gal of water for maybe 15 mins then throw them in the washer, spin out the borax water & wash your normal way. HTH Blessings ~herbalmom