Why do these people look concerned?

I took this rather unflattering photo of my parents at Yellowstone National Park during the summer of 1956, somewhere around my 11th birthday.
I guess the best way to characterize their look is "concern." Thinking back, I realize the probably spent a lot of time looking at me that way.
In this particular instance, it may have been because I was working my new Kodak Brownie camera while on crutches. I was recovering from a broken leg that I suffered in April when I rode a bicycle into the path of a Cadillac a couple of blocks from my house. I was chasing/racing a friend and I was on a borrowed bike with multiple gears and hand brakes instead of my own bike, which had one gear and a coaster brake.
The good news was that the Cadillac was being driven by one of the town's two doctors. After checking in with my parents, he drove me the 20 miles to Home Hospital in Lafayette, Ind.
My father would have been 46 when this photo was made. I'm 16 years older than that now and I think I still look younger than he did then. But then that's how the filter of memory works, isn't it?
My dad has a cigarette in his right hand. It would have been a Winston. He's wearing a two-pocket sport shirt and a windbreaker - standard 1950s tourist garb. I learned my pants pocket contents system from him, so I can be fairly certain his change and his Zippo lighter are in his right front pocket and his keys are in his left pocket, wallet in back left and handkerchief in back right.
My mother, of course, is holding her purse in her right hand. She pretty much never went anywhere without her purse. In later years, she grew more cautious and carried it tucked up in her left arm like a football.
Somewhere in the parking lot where they're standing was our 1956 two-tone green Ford Fairlaine.
Yellowstone was a very different place in the '50s. Despite warnings from rangers, people routinely fed bears from their cars. Consequently, bears are a common sight along the road. Like morons, we fed a couple of them from our car and lived to tell about it. We were in the park about two days and counted 49 bears during that time. This was also before America became litter-conscious and it was common to see people toss trash - sometimes paper grocery bags full - from their car windows as they blazed down the highway. Even then, I knew it was wrong and was shocked when I saw a blizzard of trash explode from the window of a car we were following across the Wyoming countryside.
Just to give a little more historical perspective, Dwight Eisenhower was in his first term in the White House, cars had AM radios and no seatbelts and rock & roll was a brand new phenomenon.