The only real absolute reason to have a red dot sight is for low light shooting. Iron sights will do the rest.
444 will come along eventually to respond to that in a much more appropriate and properly thought out and executed fashion... Me and my ADHD can only say this...
HUH?
Nothing works for everyone, and everybody's different, but any time a person writes off ANYTHING as being of ABSOLUTELY no use to ANYONE whatsoever, it is almost ALWAYS a statement that was not thought out clearly enough.
For starters, red dots are faster on target than iron sights, day or night, period. They allow you to keep both eyes open, focused on the target, with a more "heads up" view of your surroundings. A BIG bonus for those engaged in actual combat. On to some of the other stuff...
My list of unnecessary stuff to dress up your AR-15
Mag pull gizmos
Don't own them, don't use them, but I have handled one enough to realize that, in a real combat or LEO situation, they'd be a lot harder to drop if you were sweaty, wet, jumpy, etc...
Fancy side mount sling attachments
Side mounts are EXTREMELY useful on the AR, or any other pistol-gripped rifle. The mag and pistol grip aren't poking you in the back, and you've got the very functional option of a 3-position sling which gives the user several carry options and allows the rifle to be brought to the ready without removing from the shoulder. I've also seen this rig demonstrated very effectively for transitioning to your sidearm.
Gadgets that hook one mag to the other
While I don't own one, want one, or have any use for one, I've seen them being used quite effectively in 3-gun matches, and in videos of combat simulations with actual soldiers using MILES gear. It's faster than going for your web gear.
Eh... I could take 'em or leave 'em. Some swear by them, some swear at them. But they aren't hurting me either way, and if somebody gets use from them, then good!
$350 Surefire integrated lights (a $30 light and duct tape will work)
That's just silly. Granted a $30 light and a $20 mount would work for some (like me... I'm cheap) , but not for all. By actually using proper mounts for the flashlight, it's going to point straight ahead, in the same direction you're aiming at... all the time... Duct tape...
This one I do actually have, and it's the most useful accessory on my personal AR. My son can shoot it, my wife can shoot it, I can shoot it, and we all use a different LOP, and we're all just as comfortable as can be with our personalized stock length. Body armour would be a real no-brainer as to an application that a shorter stock length would help.
No opinion there, but I'm sure they come in handy for big-ole scopes.
Oh no, you're not a purist who thinks that EVERYONE should conform and be happy with that BROOM HANDLE known as the A2 pistol grip are you? I use the ErgoGrip myself, because it's MORE COMFORTABLE by leaps and bounds than the A2 POS that I took off. If that's an unneccessary piece that's just for looks, I suppose aftermarket stocks for bolt-actions, Pachmayr and Hogue grips for revolvers and semi-autos, as well as adjustable seats in cars are a silly bauble too.
Weapons mounted mag carriers
Well, another item I don't use or want, but I can quickly envision the "reload attached to the weapon" for a police officer who keeps an AR15 in his trunk. Bank robbery in progress right across the street from the Sonic he's eating lunch at. Perps are running to the car, firing. He pops the trunk, grabs the rifle, and has an extra 30 rounds right there on the AR without having to strap on any extra vest, pouch, etc... and also doesn't have to carry that loaded AR mag day in, day out, all day long when he may NEVER even have to take that rifle out of his vehicle.
I ain't trying to sound argumentative, and I've seen some stuff that I personally thought was just plain silly on an AR, but SOMEBODY SOMEWHERE has probably put that exact item to GOOD USE at some point.
There's more to life than just vanilla!