The bikes we rode 'back in the day' were a little different, too;
As a kid in the '80's, I rode BMX bikes, with fat little 20" tires. Even getting out in to 'the boonies' of SoCal, flats were rare, unless you hit a cactus, or something.
The 10-speeds of the '70s rode on 27x1-1/4" usually, which comes out to a beefy 32mm by today's 700c standards, usually seen on hybrids.

Like SquidPuppet said, those tires were designed for cost and durability, at the expense of weight and high-performance, but most consumers wouldn't be able to tell the difference.

Modern drop-bar road bikes usually go with 23-28mm tires, that are lighter then the old-school, and capable of higher performance. Again the trade-off is that they're more expensive, and less durable.

BikeForums is also heavily populated with people who ride a lot of bikes, a lot of miles, more so than the average American. If you ride a few hundred miles a week, you're much more likely to get a flat, than some one who might only ride a couple hundred miles in an entire year.