RDKirk wrote in post #18983966
I think backpacks are a generational thing.
They weren't used by us Boomers as kids because we never had to carry so many books home. So they were never a Boomer thing.
I am 57 and have a couple of photo backpacks. They work well for me walking through airports and while hiking. My subjects of interest are landscapes and wildlife while traveling.
BTW, I had a backpack in college back in the early '80's, too. It was the easiest way to carry the textbooks I needed. Too bad ebooks were not around then. 
PentaxShooter wrote in post #18987601
Ah, I see WHAT you are carrying. Thanks for that. However... My question was about WHY you are carrying all that gear. Is the sole purpose of your outing, while you are carrying all of that, to take as many photographs as you can?
I have Canon 80D, and lenses from 8mm to 600mm, mostly zooms. And Pentax medium format film 645N with lenses from 35mm to 400mm, mostly primes. When I leave the house with a camera, it with (generally) one photographic goal in mind. As such, I carry one body with whatever lens I will need attached. Very rarely do I go out with more than one lens; never more than two. I will never need a backpack for camera gear; I don't even use neck straps. Two hands, one camera. Seems about right to me.
I am more interested in WHY you are carrying so much gear.
In my case, I shoot both landscapes and wildlife when we are traveling -- the walls of our home are covered with enlargements of photos I have taken during our travels over the past 30 years. Landscapes and wildlife require different types of lenses, and having two bodies allows me to keep a telephoto lens on a body at all times -- thereby greatly reducing the number of lens changes. When I had a single body, if we were at a place such as Yellowstone, I would need to leave the telephoto mounted as we traveled around the park, swap to a wider lens when we came upon a landscape scene, and then chage back to the telephoto before leaving the scene. After all, a mountain or waterfall will wait for you to change lenses, but a grizzly bear, wolf or elk will not. 
I have also begun bringing a third body on some trips -- my small Canon EOS M50. It allows me to actually carry two cameras but feel like I am only carrying one. When we were in Iceland this past summer, I would sometimes hike with the M50 and EF-M 11-22mm mounted, along with a 5D3 + 24-105L. That gave me focal lengths from ultra wide to short telephoto without any lens changes. Other times I hiked with the M50 + EF-M 15-45mm and 7D2 + 70-200 f/4 IS (plus 1.4x TC). That gave me focal lengths from wide angle through longer telephoto.
BTW, I would have normally brought my EF 100-400L II on the trip to Iceland, but decided on the lighter weight 70-200 f/4 IS + TC option so I could save a little weight on my back. It worked out fine. I was still able to get shots of arctic terns and Atlantic puffins that I was happy with.
That being said, I just picked up a large messenger bag for those trips were I want to bring an intermediate amount of equipment. We are going to Key West later this winter, and I had planned on just bringing the same small kit I brought last year -- M50 plus four EF-M lenses which fit in a small shoulder bag. However, I recently bought a Canon EOS R + RF 24-105L during the holiday sales, and I really want to play with the new camera. So, I picked up a messenger bag that will hold the EOS R + 24-105L, M50 + four EF-M lenses, accessories, and have room for an iPad and Kindle (I usually carry that and maybe a Chromebook in a separate small shoulder bag).
You can never have too many camera bags when you have a variety of equipment, as you never know what combination of gear you may want to bring along.