Bingowings said:

In many ways the Jedi are more conspicuous by their absence and true to their initial description by Ben, in the premise of this film, than they actually were in person during the whole of the PT.

The lack of Jedi is the reason why the Rebels need to try fight even harder against the seemingly undefeatable Empire.

So if Ben was supposedly the last Jedi (not counting Vader), why did the general tell his X-wing pilots before the attack on the Death Star, "May the force be with you"? He must have been an adherent/believer. Was it a vaguely-recognized (and ancient) religion, but with no surviving monks? Or were they simply in hiding during the "dark times"?