Adding on to what you said, another reason older people in general can be wary of sitting down if it isn’t absolutely necessary is that it can be very difficult for them to stand back up without assistance. Especially if they are used to being somewhere with grab rails or other safety affordances.

So it might not be stubborn masculinity as much as bad knees and stubborn independence in some cases: if they stand, they can be in and out quickly on their own. If they sit, they may need to call for help.