In fairness, if it's an American point of view then it's to be expected and we probably have similar biases
Having said that, operating at night doesn't make for great theatre, whereas colour photos and films of huge box formations of B17s with all the contrails behind them, and the combat footage to go with them does
Plus let's face it, the B17 looks like a film star, which is not to take anything away from the Lancaster, but in some cases looks count as much or more than capability (think your secretary and your wife)