BOAC -you assume right. We operate mostly on big international airports,long rwys,only one or two rwys with less than 2000m.So ,maybe you have a point.
I'll try to see if there is a big difference between what you see at flaps 40 or flaps 30 .The difference in airplane boddy attitude is 1.7 degrees (3.7-flap30 ; 2.0-flap40 for 700 series) and the main gear touchdown poin (no flare) is at 657' (flap30) or 683' (flap 40) .So ,not a big difference,from this figures,i guess.Also ,you can see,almost 30' less in air when using flap 30
But ,again,you may have a point.Happily,we get to chose between 30 or 40.
Brgds alex