Early gaming walked the same path. The assumption in those days was that, since it was all fantasy anyway, why worry about historical accuracy? Sure, D&D borrows most heavily from the medieval period -- OD&D even bills itself "Rules for Fantastic Medieval Wargames Campaigns" -- but that's not the only period from which it borrows. Anyone who knows the details of the Greyhawk or Blackmoor campaigns will quickly see that neither was simply an imaginary medieval Europe with monsters and magic. What would be the fun in that? Gary and Dave saw inspirations in a lot of different sources and incorporated them into their home campaigns without any concern about whether it was "realistic" or not.
The only concern that matter was fun and so those early campaign settings are filled with lots of oddities and strangements, at least to modern gamer eyes. My feeling is that such things add to the charm of those settings and help establish that you're playing in a fantasy world whose rules , such as they are, do not necessarily mirror those of our own world. That's sometimes forgotten, which is throwing some anachronism into your adventures can often serve a useful purpose.
Of course, not everyone has the same sense of how much anachronism is too much. As referees, we must each draw our own lines in the sand. I tend to be pretty lenient, drawing the line primarily at anything "jokey," which is to say, at anything whose presence makes my players laugh (unless laughter is my explicit goal). By way of example, here are a handful of anachronisms I don't mind in my fantasy worlds and in fact often include:
- Tobacco: Why invent "pipeweed" or some other replacement when you can have the real thing? Every fantasy world needs tobacco for wizards' pipes, if nothing else, and cigars were made for the Guildmaster of Thieves or corpulent merchant princes to wave around dramatically.
- Eyeglasses: Yes, these did exist in the late Middle Ages, but they weren't widespread or as effective as modern lenses. More importantly, there were no sunglasses and I have no problem with them in my fantasy worlds. Heck, there's already precedent for magical glasses in D&D anyway, so why not mundane ones? I also seem to recall the Gray Mouser wore shades on occasion, though I may have imagined that.
- Powdered Wigs: Nothing says pompous official or effete nobleman like a powdered wig.
- Eating Utensils: How can you have a proper bar fight if someone can't grab a fork off the table and try to stab some half-orc ruffian with it?
- Gender Equality: Believe it or not, there weren't female warriors in the Middle Ages or indeed pretty much anytime in history. Funny that.