Should, would, could.....
None mean MUST
I live on an airfield and so can go flying any time I want - no "is my journey necessary".
In fact, if I was in England, then I might be prepared to take my chances with an over-zealous police officer who wanted to stop me from flying to my daily exercise, rather than driving to it.
But I have too much respect for the NHS and fellow citizens. So I am grounded and the airfield users are - except for the suggested exemptions, most of which don't apply to the type of aircraft based here.