>>>Dave may be right about some societies, but the ones I know about which have surveyed their members do NOT find that the bulk of members are former employees only joining for fellowship with guys they worked with.
Tony's hit something here
Some UK railway societies follow companies that ceased operations in 1948 and several more focus on companies that lost their separate identities in the grouping of 1923. I suspect there are not that many former employees left from before 1948 former and possibly a mere handful who started their careers before 1923.
The key difference however is that many of these organisations were formed as modeller-oriented societies decades after the companies they follow ceased to operate; some have formed relationships with various museums and societies as well, but the great majority of the membership comes from modellers (of both active and armchair varieties) or modeller friendly historians.
Perhaps this does run the risk of skewing the way history is represented? Modellers have a natural fixation on the physical plant and appearance and, while articles on Highland Railway luggage barrows and platform seats or Sacramento Northern trolley poles and collector shoes are essential reading for the serious modelmaker, they might not always be a topic that appeals to social/serious historians.