I've got homework to avoid, so I'm going to suggest some answers to a question posed by Unfettered Blather and backed up over at Man Bytes Blog.
The question at hand is: "Now, please explain to me why future weapons will have less options than weapons available today?"
1. Technology implementation is not consistent across any culture. The things we use everyday do not correlate with the most advanced tech. In addition, often the most advanced tech can only be used at great expense and only rarely. Why do most firearms still use combustion technology that has been around for at least 700 years? Why isn't caseless ammo standard? It isn't a question of can you implement a technology, but can you mass-produce it, will it be reliable and can it be made for least cost (both labor and materials)?
2. What does Faster-than-light travel have to do with military weaponry? Seriously. Our submarines use nuclear reactors that allow them to stay submerged for months at a time, but that has nothing whatsoever to do with the grunt in the field. Not only is implementation not consistent, but neither is advancement. There are often limits on knowledge that are not immediately apparent.
Most military organizations are conservative when it comes to changing tactics or adopting new machines. Patton was laughed at for championing the usefulness of the tank in World War I, and yet it became a pivotal weapon in the next World War.
3. All those fancy attachments don't necessarily make the weapon better.
Consider the M203 grenade launcher attachment for the M-16. First, you can't fire the rifle when the grenade launcher is attached. This is because it uses the barrel as a place to build up gas pressure to launch the round. Second, you have to reload after every shot and, even though it's a grenade, you can still miss. Third, you need extra training to use it and even more training to use it well. The M203 uses a leaf sight, which is only accurate if you know what you're doing, and even then you have to account for wind, recoil and other battlefield conditions.
Think about this: The M16A1 service rifle had the capability to go fully-automatic. The current service rifle, the M16A2, does not. This is because allowing full auto led to grunts spraying rounds without regard to where they went. It wasted ammo, weapons deteriorated faster and was less effective in combat. This is one of those clear-cut instances where fewer options actually resulted in greater combat efficiency.
4. In addition to specialized training, attachments require their own special maintenance. Yes, let's give everyone a laser sight. How long do you think that's going to last, crammed into a grunt's pack with sand and dirt and an entrenching tool, thrown into the back of a Humvee and dragged along the ground as the grunt low crawls into position? An improperly maintained and calibrated scope is less useful than half-decent iron sights. And if you can count on anything, it's that any equipment you send into the field will not be properly maintained or calibrated.
Here's a funny story. The Marine Corps was looking for a new pack to replace the ALICE pack, a canvas bag with a metal frame that's been used in one form or another since the 1970s. So a company came up with a super-advanced pack that was ultra-light and waterproof and modular with a durable plastic frame. The pack went through the company's own rigorous testing and then it was released to select infantry units.
The damn thing fell apart. The grunts rejected it 100%. The vaunted super-tough material ripped in a day's time after normal field punishment. The plastic frame snapped. The modular pieces got lost all the time. Despite using "advanced" technology, it was worthless.
5. The two most important characteristics an infantry weapon needs during a ground invasion are durability and ease-of-use. The weapon shouldn't break and any idiot should be able to get steel near a target. Every time you add an extra function to the weapon you make it harder to maintain and more difficult to use.
6. Fancy toys don't beat unit cohesion, smart tactics and solid weaponry. Look at our current state of affairs in Iraq. We have plenty of fancy equipment at our disposal and it doesn't matter. Even if we outfit every grunt with a computerized tactical HUD, auto-targeting weapons, thermal scanners, etc., it wouldn't do a damn thing against an IED stuffed into a coffee can.
So the short answer is: Maybe those options exist but aren't worth the negative factors of implementing them.
Or it could be game balance, I guess.
As a small illustration of my point, Rainbow Six Vegas has lots of cool options for each weapon. There's thermal vision, different kinds of scopes, silencers, firing modes and laser sights. Every time I'm in a firefight I have to take the time to sort through all the options available while I'm responding to real-time threats. For every time one of those fancy doodads is useful there's another time when it ruins the assault.
The laser sights tip off the enemy to your location. The 6x scope limits your vision. The thermal vision picks up all hot objects in the area. Full-auto has uncontrollable recoil.
Which means that there are plenty of times that I try to get all fancy when just shooting from the hip or going to iron sights would more than suffice.
I end up at the Reload Last Checkpoint screen a lot.