To expand on what Schmange said. The first call will not necessarily go to the best guitarist but the one who can be: 1) reached at short notice, 2) will be reliable i.e. turn up on time and sober, 3) gets on with people.

Who wants to work with a virtuoso who's head is so far up there own ass they will never see daylight again ?

But man it is a hard life.

Oh yes, also learn to teach to subsidize studio work