This is a situation that has a simple solution. Ride a long wheel base recumbent. My RANS Stratus has no "top tube", and it is virtually impossible to be thrown over the handle bars. It is unfortunate that the general public is herded onto diamond frame bikes. Most LBS will have little to do with a recumbent. What I see is that now a lot of baby boomers are sold a high end mountain bike. They ride it a dozen times and find out that they hurt, and if hills are involved, they have to work harder than they thot they would. So what happens is the bike gets hung up in the garage for 5 years, and then sold for $50 in a garage sale. How ever if they had bought a recumbent, they would have had no pain, and might have kept on riding. Also if they would have crashed, they would probably have just landed on their side on their rump. Probably a little road rash would have been the most damage to the body.

BTW I have never been thrown over the handle bars on a diamond frame bike, but when I was a kid I did hit the top tube a couple of time.