Well that's amazing for you and you're clearly very proud of yourself.
There are a lot more barriers to exercise than you seem to think.
I might have 30-40 minutes spare, but by the time my work day is finished, my children are cared for and I have done my other hobbies which benefit my mental and physical health, it is very difficult for someone with chronic fatigue to use that 30 minutes to do exercise.
I absolutely do not have time to spend days recovering if I accidentally push myself too far and end up triggering my medical problems, which also cause the chronic fatigue.
I can't run due to joint problems. I don't like to swim because the chlorine really irritates my eyes and my asthma. Gym classes are tricky because I have to be free at the right time to go which is not often. I'm generally limited to things I can do at home in my own time, and can only do that when my small child isn't going to come in and try to "help".
Add in ADHD and the difficulties around executive function, the stress of trying to decide what exercise to do, work out what to wear, make sure it's been laundered and put away where it should have been, then factor in showering and getting dressed again when I get home- that's a lot of steps to work through.
I'm happy for you that you are able bodied and can use that 30-40 minutes, but if you ask me to join you and I say "I don't have time," I mean all of the above, but am assuming that you would rather use YOUR time for something more valuable than hearing it all.