[MENTION=302603]bikemig[/MENTION]'s post (no. 2 above) explained the reason for the gear spread perfectly; speculations about whether or not the riders using those gears were ignorant are unnecessary.

My first 10-speed bike was a Raleigh Blue Streak---got it for my birthday in 1963, I think. It had Cyclo-Benelux derailleurs that were very limited in their chain wrap capacity. They worked best using the outer chainring with the middle and outer two sprockets and the inner chainring with the middle and inner two sprockets.

Given that kind of compulsory shifting pattern, Charly Gaul's bike's gear development described in the first post clearly makes sense, with two two-tooth jumps followed by two three-tooth jumps.

And Jean Dejeans's PBP bike's one-tooth jumps in the smallest sprockets followed by an abrupt jump to the largest two sprockets also make sense if you know that the Paris-Brest-Paris race was by far the longest race on the European calendar and, with the exception of a few sharp rises, was nearly dead flat.

(How long was the race? In 1948, according to Wikipedia, the winner finished in 41 hours, 36 minutes, 42 seconds.)

Grinding along in a high gear was what they did in those days. Remember, most of the racers were coming from a tradition of racing through the Alps and Pyrenees with single-speed bikes.