I think what has happened in many cases, is the general progression and mutation of airsoft naturally. Thunder Cactus really touched on this in his post. Airsoft is a game, and/or a series of games that have been adapted into many personalized tangents, i.e. Milsim, reenactment, speedball, role play, etc. For most players, modern military scenario is the best and by far the most dynamic way to play. What the hardcore gamers have run into, is that unless your doing strict training ops, then not everything translates over well from military into airsoft. I like to think that the more mainstream style of play is slowly making it's way into a more concrete fashion, somewhere between a progressive sport and military simulation. As a player, the military aspect is paramount as the base framework for any game. You can use this effectively in communication, objectives, storyline, tactics, etc to maximize the experience. The flip side however is this; I play myself as an airsofter, and at no time do I think or portrays soldier. I'm here for the competition, and extreme sport aspect, not to drill and train for an eventual nothing. I know my enemy will return once I shoot him out, I know my gun can miss at fifty feet even when pointed straight, and not all military tactics will work against an opponent that doesn't have to worry about death or dismemberment; and therefore my battleplan must take into account all of these things.
Run real caps, leave bodies where they fall, no re-spawn reinforcements, strict objectives and timeline; that would be closer to military simulation.
In essence, it really comes down to the balance between the two aspects, and how it adapts over time. You want the realism, and you need the fun factor.
ďREALITY IS LIKE A STONE. TO MANY ITíS HARD AND COLD, THEY CANíT HUG IT OR EAT IT, IT ONLY FRUSTERATES THEM AND DOESNíT DO THEM MUCH GOOD. TO OTHERS ITíS STRONG AND DEPENDABLE, YOU CAN BUILD WITH IT, BUILD UPON IT, OR WORK WITH IT, ALSO USE IT TO SMASH PEOPLE IN THE FACE.Ē