SOCIAL CONSTRUCTION OF SEX ROLES. "“Females tend to be better at fine manual skills such as threading needles to which they are more suited than men because of their small fingers.
“If you ask them to do small, fiddly jobs they are going to perform much better than men." That's according to a (male) psychologist at Northumbria University, quoted in this bit about why men can't wrap non-Euclidean presents. Evidently the good psychologist has no colleagues in the Gauge O Guild.