Yes, I understand your viewpoint. And I agree with you - I personally also generally prefer when all options/buttons are easily seen at all times.
I also do a lot of thinking about UI design, one thing I want to avoid is getting the UI too cluttered, and avoid too many levels of options and sub-menus for the user to wade through.
I often get requests from people to have a certain option implemented, but I think very carefully about each one, to evaluate if it is important enough (to sufficient amount of people) to have the UI burdened with another option. Some things can also easily cause confusion. For example, if there was an option to permanently hide the UI, someone might accidentally activate it and not know how to get it back. And, on touchscreen only devices it is not possible to keep the UI hidden at all times. So the best compromise I found, suitable for most users, on most devices, is the one I implemented.
I want the simulator to be as easy as possible to use, even for people who have never flown an FPV quadcopter in their life, who have never been close to doing a Betaflight setup for example. Still, I want it to be flexible enough for advanced users too, so that everyone can find good use for it regardless of their skill level. So, as you understand, there are a lot of factors to take into consideration here.
With all this said, I might consider adding an option in the custom settings for "keep UI always on". Thank you for your feedback!