Mainly for two reasons.
1. Goff is NOT McVay's guy, he didn't draft him nor does he have any idea at this point how long it will take Goff to be what he needs him to be.
2. McVay knows Cousins and Cousins knows McVay. Supposedly McVay invested a lot of time in Cousins to get him where he mastered the offense.
That has value.So IF Cousins doesn't get signed in Washington and Goff doesn't demonstrate the improvement on the field that McVay wants to see, I could certainly see interest there from the Rams.
IF McVay had drafted Goff I would be more skeptical....but he didn't!
Best,
Laram