I found it extremely hard to use the fly on briefs, but never thought of lowering the underwear unless I was wearing sweatpants. I haven't worn sweatpants since 8th grade gym class.
How do you lower your underwear band if you're wearing jeans, khakis, slacks, etc. I use a belt, so I'd have to unbuckle that, undo the button, unzip the fly, and then lower the underwear waistband. Is there some trick I'm missing, because it seems like a lot more work than using the fly (at least with boxers, which I wear exclusively). Though even some boxers are difficult because the hole is too small. So I just never buy that brand again.
I had really nice boxer briefs but there was no fly, so I stopped wearing them as they seemed non-functional to me. It probably just comes down to preference though.
Interesting over 70% do not use the fly. My experience at the urinal is most people do use it, though I never look directly, only peripherally and only sometimes.