The OP has stumbled onto some odd gearing, and developed incorrect opinions as a result.

Through the 50s, 60s, and to an extent, 70s, small differences in chainrings were common. Something like a 47-50 would have been typical. The freewheel would rarely have had anything smaller than a 14. 12 and 11 cogs didn't exist, for practical purposes, and rings much larger than 50 were specialty items for motorpacing and such.

Into the eighties we saw bigger differences in chainrings: 42-52 was absolutely typical. The smallest cog at the back would be a 13. Later in the decade, and early in the nineties, the big chainring was most often a 53, the small ring a 39, and the smallest cog out back shrank to a 12. It was only in the late nineties and into the new century that the 11 cog became common, along with "compact" cranksets with a 36-50 or what have you. So the 55 tooth on the OP's Bianchi is surely an aftermarket item, and the 11 cog on his Motebecane is completely incorrect for the era.

Essentially, over the years low gears have gotten lower, high gears have gotten bigger - on racing bikes. A professional racer of the 1960s would have had absolutely no use for our 53x11s, as sprinters at the time stayed in the saddle and spun a relatively small gear at 180 rpm. As for the hills, well, the professional racer then had no more reason to use a 34 cog than does the professional racer of today, so neither their nor our racing bikes come with them. Touring and recreational bikes were available with very low gears (26 ring and 34 cog, for instance) as far back as the 1920s, but those bikes have never made it to American shores in significant numbers, so few folks seem to be aware of them.