I don't think my parents underestimated childhood shame. They made conscious use of shame and embarrassment over nudity when they punished me.
Between the ages of four and six, my usual punishment was a bare bottomed "switching." Mom or Dad would take the switch off a hook on the kitchen wall (the switchings always took place inside the house, in our living room), and order me to stand still. They'd unbuckle my belt and pull down my pants and underwear, leaving them wadded around my ankles. Then the switching would begin.
By then, I knew it was "naughty" for anyone to see my bare bottom or penis, so I hated being naked from the waist down as much as I hated the pain from the switch hitting my bottom. My sister (three years older than I was) always ran into the living room to watch, unable to contain her glee at seeing me stripped, and the way my little penis would shake with each smack of the switch to my bottom (she thought my humiliation over the latter was especially hilarious.) Mom and Dad never told her to leave while I was being switched; in fact, they seemed to notice how much I hated her laughing at my shame. They always said, "Now, you remember this so we don't have to do it again!"
Just for 'good measure,' they'd force me to spend a post-switching half-hour in the corner with my pants still around my ankles. My sister continued to run in and out of the living room, just to squeal some more at my bare hips and cock, and my embarrassment.
I think I felt more embarrassed having my pants down than if I'd just been naked. It seemed to make a point of shaming me by everyone getting to see my hips and penis, in particular.
On one occasion, a neighbor came over to visit and saw me like that, standing in the corner, naked everywhere it counted. I never forgot her smile, or how she made no secret of taking in all the details, or her smug advice... "Well, you be sure to mind your mom and dad, so they don't have to do this again."
But they always found a reason.
Even after we were older, and Dad had (mostly) shifted to punishing us with two-hour (clothed) stands in the corner, he still made threats of naked humiliation to keep us in line. If my brother and I got too rowdy in the car, he would threaten to strip us naked in public.
I recall vividly an experience in which Dad lost his temper as my brother and I were goofing around in the back seat, distracting him in heavy traffic. He told us that we had three seconds to settle down, or he was going to pull over to the side of the to road, pull us out of the car, pull down our pants "right in front of everyone" and spank us. (I was about 10 at the time, and my brother would have been 8.) And he clearly meant it.
We were both horrified, and didn't make a sound for the rest of the trip.
It was clear that the main point wasn't the physical pain involved in the spanking. It was showing us who was boss by threatening us with public sexual humiliation.
None of this was even remotely "fun" when I was a kid. But things change...
It's probably because of all the bare-bottomed spankings and being on display as a kid, that I still have a thing about having my pants pulled down, and about being bottomless. Given that my girlfriends and wife # 1 often told me about their kinks (and I would try to give them what they wanted), I would sometimes ask them to humor me with my stripped butt fetish. Like my girlfriend when I was 18, who would come over evenings where I was house-sitting, gleefully strip down my pants and remove and keep them, and tell me I had to remain bottomless the whole evening (even while we watched TV)—with everything where she could see it—if I wanted her to suck me in bed that night. (For me, that was a win-win.)