The reasons (as far as I know)
They dim the lights so that the pilots don't get any backscatter from the ground which might interfere with the delicate task of not smashing hundreds of people into tiny pieces.
The blinds thing is so that in case they do fail at the primary task, and the plane is less than functional, any light from outside, be it sunlight or searchlight, or even flames from the fuel tanks, will light up the inside to allow better vision for the people trying to escape.
But then I may also be wrong...
(badgerlikespeed, Wed 19 Oct 2011, 15:38, 1 reply)

Compared to the landing lights,
is backscatter all that much of a problem? (I ask that in earnest: I wouldn't have thought so intuitively, but may be wrong.)

The blinds thing, as with the explanations ^up there^, may have something to it, though it seems (again, intuitively) a bit tenuous...
( Enzyme is powered by sunlight, Wed 19 Oct 2011, 15:42, closed)

Perhaps not under normal conditions
If it's foggy/raining hard/snowing then it might have a greater effect. Remember how hard it is not to be distracted when driving in the snow?
( MatJ LOOK, Wed 19 Oct 2011, 17:30, closed)

In light aircraft at least, you're meant to turn stuff like strobes off in cloudy/misty weather, so that you don't have the whole sky as far as you can see blinking at you.
(gordonjcp, Wed 19 Oct 2011, 17:40, closed)