One way to think of it is that the connections you make in the workplace run in one direction. The connections you make throughout the community run orthogonal to that. Combined, the two build up the social "fabric".

However, when you shift the majority of connections to those made through the workplace, you end up with just a bunch of connections running roughly parallel to each other. Not so much a fabric as a pile of string.

Probably many flaws to this analogy, but that is basically the idea of "third places". That you need somewhere where people interact based on something different from what they do for a living or who their direct family members are.

My mother was active in my school, reading exercises, schooltrips and fairs and the like.

A lot of the mothers were. Actually we only had 6 teachers, for 6 classes/grades. No other personel ( one of the teachers was the 'head' ).