I think this one explains why the mass adoption of the bicycle took so long. Before the era of precision manufacturing, each mechanical device had to be hand-a

I think this one explains why the mass adoption of the bicycle took so long. Before the era of precision manufacturing, each mechanical device had to be hand-assembled by an expert machinist who fine-tuned crude parts into a working device - meaning there were no drop-in mass-produced replacement parts. This would make maintenance and construction impractically expensive.