I have been lucky enough to get my hands on a lot of vintage road bicycles over the past ten years or so. At first, I bought the incredibly light BS thinking the my higher enders were less than 20 pounds. Not so!
Generally there are four categories of weights.
Department store entry lever = 30lbs+
Bike Shop entry level 25-35lbs
Bike Shop quality bikes 21-25lbs
I have not measured the weight of all of the bicycles found over the years. In fact, I started measuring weight about four months ago when I bought a digital scale. I was surprised at the results. Today, the lightest bike in my collection comes in around the 22lb mark and that includes the weight of the pedals mounted every time.
As for weight making a difference? You bet it does. Swap a set of clincher wheels for a set of sew-ups and compare. The two to three pounds saved will indeed be felt in the seat of your pants when out riding. Also, to get weight down, one must opt for good quality components which are not only generally lighter, but they work a great deal better in most cases. Again, this adds positively to the feel of the bicycle.
So does weight matter? To me it does but if I am looking to significantly lighten up a bike, I loose weight myself and guess what, the bike is better to ride.
On a final note, I recently acquired a full Columbus SLX Gardin Anniversary. An incredible bike for its age and very light. Sadly, I am too heavy to ride the bicycle. My weight and strength flex the frame set like crazy.
So if you goal is to have the lightest vintage road bicycle around, spend lots of money and don't ride it a lot if you weight more than 170lbs.
Just an old man's opinion, of course.