the body can only express reactions to too much stress in so many ways. all that stuff is connected and it all influences each other in one way or another. For some it's a dysfunction in the foot bones themselves. Whether it's a dropped arch, over pronation in their gait, or shoes that don't allow bones of fee to move naturally. It can all affect the tissues in the foot and when it's bad enough the body can only respond in so many ways.
For others it's calf/achilles problems, for others it's higher up, hamstring or hip. Had another guy scoff at that idea when I told him I added hamstring work. No way he said, ,so we did the old school straight leg raiser and a little dorsifelxion to his foot and watched his hamstring light up and I said, still think it's not connected? Tend to see it move higher up the chain the more sedentary the person is generally speaking.
what can cause inflammation in the bottom of the foot? chronic stress, acute trauma, poor diet, weak soft tissue to begin with, work surfaces, footwear, medications etc. Toss in other variables, like we all have different thresholds. If our tissue doesn't hit a certain threshold, you don't feel it anyway and if you don't feel it, you likely don't care. Make a change to one variable on an individual it might be enough to bring it under threshold and they're happy as can be. Lots of people have foot dysfunction with or without orthotics and
orthotics are easy to try, assess the foot and make 'em. Some like rigid and have lots of good reasons for it. Some like one's that have more flex and have good reasons for it. Many people have been helped by both. Many have been helped by neither.