ExFlyBoy5
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
When I was 45, I ruptured two discs in my back and I was almost paralyzed for a week - and it took another month to get a decent range of motion back. Good thing we lived in an apartment building with the rooms all on one level.
More recently, I broke both my arms and although that didn't impair the ability of my feet to take me from one floor of the house to another, having one arm in a sling and the other not functioning well left me quite uncomfortable navigating stairs for a couple of weeks. So I know from personal experience that one of us could experience periods of time when going up or downstairs frequently would be problematic. Currently, we've also got parents who visit and have some difficulty with stairs.
It is easy to imagine scenarios where someone could experience temporary or long-term limitations on their ability to manage stairs - and yet still have many years left until their "ultimate" retirement from this plane of existence: e.g. knee or hip replacement surgery, a serious illness impairs their cardio capacity, balance or energy levels (e.g. cancer treatment, COVID etc).
That said, I don't feel the need to have a master bedroom on the main floor - just a room that could serve as a bedroom and at least a powder room that could be converted to a full bath if physical limitations were going to require a long-term solution.
This x1000. My DW is barely in her 40s but has had 3 spinal surgeries in the last 10 years so stairs are really a no go for her. Plus, you never know when something might happen to make getting to the second floor nearly impossible and that condition could be chronic and last many, MANY years. Nothing wrong with a second floor, but I certainly wouldn't want it to be where my primary sleeping/bathing area could be inaccessible.