I’m 190lbs, 5’9", size 14 jeans, so I’m no lightweight and looking at the size of my butt and thighs that contact area is far larger than the panels on my all purpose hunt seat saddle. Which, although being a great fit for my horse, does make her back sore on longer rides.
So I started searching for a saddle to start trail riding in and conditioning for a clinic and I bought a Reinsman Flex Tree Trail saddle. Nice huge bearing panels, comfy fit, flexible tree. The horse was happy after a 12-15 mile ride, although she picked her way down hills I thought that was normal. Just being careful, right? Then I tried a friend’s Torsion saddle and while wholly uncomfortable for me, all of sudden my horse was going downhill ears forward and booking. Wow. Obviously she’d been having shoulder pain that I knew nothing about. I knew I had to make a change.
Then I rode in a Freeform and I loved it, horse loves it, no more sore backs or shoulders, better stride, all in all much happier. I’ve tried other traditional saddles on her, a Benz dressage saddle, a Passier, and several other western saddles and a couple other all purpose saddles with every pad known to mankind. Some were altogether rotten, some fit just fine for regular working arena rides, but none have been comfortable for long rides except the treeless Freeform. So if you’re so terribly against treeless saddles please, I would LOVE to find a nice treed saddle that my mare would be happy in and my less than stellar riding friends could amble down the trail on her in but frankly, I don’t think one exists! And please tell me why she’s so happy and comfortable in a treeless and so miserable in any of the other traditional saddles I’ve tried. Each horse and rider is an individual and a team and what works fantastically for one pair might be abuse for another. I would not recommend going treeless on a horse with a ton of spook or for a rider with less than ideal balance.
So saddles evolved over time with trees. What drove the innovation? Bigger weapons, more armor and basically the need for a more stable fighting platform. Sorry, but I don’t plan to joust in my saddle anytime soon. If I can mount from the ground it’s stable enough for me. My primary concern in the choice of my saddle is my horse’s comfort, not how far over I can lean to decapitate a fellow competitor with a broadsword. 
It just wouldn’t be sporting.
