I agree, but a 2% difference can add up over time and bike and gear weigh savings can be far greater than 5 lbs when compared to a LHT with 4x panniers and a handlebar bag. If bike and gear come in at 40lbs rather than say 80lbs you'll really notice as it might be a 10% to 20% difference.
In fact the OP's question about "lowest high gear" that you can happily ride is certainly a function of the rider+bike+stuff total weight.
Lighter totals will probably tend towards wanting higher top ends. Although even with a light bike I'd be happy at 70" as I don't see the need
(or have the stamina) to travel along on the flat all day at anything over 20 mph and I don't mind if I spin out on the downhills.