Despite some misleading pictures shared on social media, if you do an apples-to-apples comparison (e.g., a 1972 F-150 and a 2023 model with the same bed size), they are about the same length. The differences are vastly better driver safety and fuel economy.

Even the differences in height are often overplayed by making bad-faith comparisons: https://i0.wp.com/www.curbsideclassic.com/wp-content/uploads...

The main difference is that nowadays, there are more factory and aftermarket configuration options available, and people have more money, so you see more people driving heavy-duty trucks with 35,000 lbs towing capacity, which have big engines and thus are rather beefy. But conversely, you also see more people buying small trucks with "stub-length" (4-5 ft) beds.

It's interesting that you don't really have a market of mini-pickups that are seen in Japan, but that's probably partly a matter of weird fuel efficiency regulations, of import restrictions, and cultural factors (few people in the US want to be seen riding anything golf-cart-sized, and it's not exactly a guy-only thing.)