It's a bit different than that analogy would suggest. Learning things piecemeal can leave strange gaps in one's knowledge, in my experience. A book is often much quicker.

People still exercise and make up physical activities to compensate for the more sedentary lifestyle, though.

There are quite a few people who do exactly that, including in modern Western countries.

Oddly enough I do a little bit of computer consulting for one such person.

Horse and cart might be antiquated and slow, but my god are they so much cheaper and more reliable than the modern car.

Many parts of the world still rely on horse and cart today, even modern societies.