Both

I initially started full-time at age 11. That's when my parents first gave me control of my clothing purchases and a budget. To make a long story short, my very first acquisition was a pair of Levi 501s, which I decided I'd wear w/o UW, both for comfort and economy. Levi 501s w/o UW were my 'uniform' for most of the next 2 decades except for shorts in Canada's often brief summers. I have several pair of UW, but the only time I wear them is to UW parties at clubs, etc. Sometimes it's the transparent ones or my bright red jock strap.

When I think about it, I had always worn shorts of one kind or the other in summers since infancy. I don't ever recall wearing UW with them. Nor did I think much about showing genitals. I recall my mother talked to me when I was ~12 years about 'showing.' She prefaced it by 'should you care, you are!' Nothing else was ever said at home. What I wore, if anything, was considered my decision and prerogative.