Why are people over the age of 40 so bad at video games?

[RecondoJoe]

I'm 37 years old and I've already seen a massive decline in my own gaming performance over the last 10 years. But I also have a lot of friends who are 3-4 years older than me, and who used to be great at games like WoW, and now suddenly they can't play it at all. Like some of them have began mouse-clicking and keyboard turning and get super frustrated and throw tantrums doing basic stuff that they used to do with ease 10 years ago...

Refusing to try a new class or spec because it might be too hard, playing with sub optimal builds because it requires them to press less buttons...

... like what happens to the human mind between the ages of 30-40 that make people fall off so hard when it comes to pc gaming?

I really am ranting because it's frustrating that these people still want to play with me, but make the game miserable to play and throw a tantrum when I point out that they are getting massively out DPS'd by the healer and tank, and I can't take them in raids or groups anymore because they rage quit halfway through the instance, saying that the game is too easy to hold their attention despite them being dead for most encounters and at the absolute bottom of the damage meters.

Like do I really only have 3 years left before I become too senile to game?