The majority of the people who want chambers are parents who are buying for children with autism, lyme disease, TBI, and other injuries where capillaries in the body are broken. Some people use HBOT therapy for bone repair. But, only the higher pressure chambers can be strong enough to actually help bone. For those who have more severe health issues, if using 1.3 ATA chambers for long enough time (you can us an oximeter for under 20 dollars. You put your finger in it and it gives a reading on the oxygen in the blood. They are actually pretty accurate. Everyone in my opinion that has a hyperbaric chamber should have one of these.
For general health, those that have not had very recent traumatic injuries can use a 1.3 ATA and I don't find a need for higher pressures such as the hard shell chambers that go to 5 ATA.
The most popular chambers for those not looking to go over 1.3 ATA are the Oxyhealth Vitaeris 320 and the Vertical Dive chambers. For ease of use, many people don't want to use straps unless they want to use it for higher pressures. Some strap type chambers have straps even though they only go to 1.3 ATA only because the windows will balloon out. The Oxynova chambers that go to 1.4 ATA do not have straps but are made of Teflon. Many people don't buy them because even their 28 inch chamber costs 3 times as much as the strap type. Their 28 inch chamber sells for nearly 18,000 dollars. The Dive Pro chambers cost much less due to having straps that make the chamber strong enough to go to 1.5 ATA. If someone wants to have a really strong chamber without straps with Teflon it will cost a high price.