Highly recommended - rewarded ten to seven hundred times
Simply recommended - rewarded as a single good deed
A command is a command. We are punished if we are not able to do it, whether there is a valid excuse or not.
Islam does not obligate a person to do what they are not able to do
If a person is unable to pray standing, he doesn't have to pray
Islam is a religion that contains ease and convenience.
If a person is unable to do part of an action of worship, the whole action of worship becomes non obligatory.
Since it may lead to extra prohibitions/obligations
People before us have fallen into this error and been destroyed because of it
Since we too might be destroyed if we do this
It is not the job of the scholars to answer people's questions
Only this one
Both Al Bukhari and Muslim