I’ve posted these thought in the XLBS forum too but I thought I’d add them here too.

Picking a historical period is no different to picking either a genre and then an IP and finally a faction. Will I play Fantasy, Sci-Fi or Zombies? Will I play Warhammer, Kings of War or Lord of the Rings? Will I play Orcs, Elves or Dwarves? Etc. Questions like scale are common to all types of miniature gaming.
As to the model ranges, previously everything was in metal, the quality of the models varied greatly because there was no ‘GW’ pushing the historicals manufacturers to ever higher quality levels. It’s only in relatively recent years that Warlord, Vitrix, Gripping Beast, the Perry’s and Fire-Forge have moved into hi-res resins and then plastics, long after GW moved Sci-fi and fantasy there.

I think it’s easy to forget that GW Historical rules pushed into the historical games world and could have easily dominated the market had they miniatures to back those rulesets. Warlord, the Perrys and most of the big historical rules sets have GW designers/sculpters at the helm.
The number of rivets argument is ridiculous too. If you paint a Space Wolves army bright pink, people will comment that it isn’t very accurate. If your Elves all have blue skin, people will ask what the hell happened to them. In ‘real life’ everyone knows Orcs are green, that’s why they are called “Green-skins”! Companies like GW spend loads of time creating colour schemes of uniforms for players to follow.
The historical reality is that the mass production of uniforms in a factory doesn’t happen until the mid 19th century and even then there is massive variation. You only have to look at German uniforms in WWII to realise the variation in colour, design, etc even within the same divisions, despite being ‘uniform’.
In regards to the ‘Grognard’ issue, historical wargamers have traditionally replayed historical battles, Zama, Cannae, Hastings, Waterloo, etc. The funny thing I’ve seen with these battles if you want a different result you need to set up differently, manoeuvre differently, etc or you get the same result but then I’ve watched historical gamers almost go into melt-down when a player departs from what happened in history. Don’t get the point myself. Sci-fi and Fantasy never really had that restriction. You were fighting battles that never happened in worlds that don’t exist. Having said all of that, the worst meltdowns I’ve seen have been in miniature games that weren’t historical gaming. The historical gamers got frustrated when history didn’t repeat itself in game, a rant about dice and rules and then back to the game. Some of the meltdowns in 40K and Magic that I’ve seen over the years have been ridiculous, dangerous and bordering on violence.
With the advent of larger scale warfare, such as the world wars it’s been easier for historical gamers to abstract conflict and not pin themselves to specific battles. There were so many theatres of conflict in the world wars and so many battalion sized battles in so many locations that the range of what may have happened is greatly broadened. WWII Russians fighting Brits? Maybe it’s an accidental exchange in Afghanistan. Germans versus Japanese? It could be German trainers and German equipped Chinese troops versus the Japanese in Shanghai, etc.
It’s the same in any game world. Anyone familiar with the Warhammer World would have had to ask themselves how often Ogres and Lizardmen would have fought, or Dark Elves and Chaos Dwarves, Chaos and Tomb Kings, etc. In 40K the Tau Empire is tiny and yet they seem to constantly come into contact with every race in the galaxy. Marine Chapters situated on a single home world seem to cross the galaxy, pass possibly hundreds of other chapters and threats to the Imperium to fight races they would feasibly never come into contact with.
Historical gaming is growing. Slowly. Games like Bolt Action, Flames of War and the ability to go beyond just replaying history will continue to broaden the number of people playing historical miniatures games.