That is only immediately true. Sometimes these nons begin to feel mortal and need to reconnect with their religion, just as some non observant Christians or Jews do. The effects are different, though, It turns the nonobservant Moslem into a fanatic observant Moslem with the fervor of a convert. The difference between Moslems reverts on the one hand and Christian and Jewish reverts on the other hand is that Moslems then have to prove their new dedication by killing infidels. Chrstians and Jews don't do that sort of thing.
And nons also have children that sometimes feel the call of their religion.
There are many good Mohammedan doctors hereabouts. They all go to the mosque and listen to the Wahhabi imam. Some of it must have effect. I do not let my wife go to a Moslem doctor. Will he feel the call? when? what will he do?
How do you identify a Muslim Doctor in America?