I'm fairly sure it is because as we grow older, we habituate.
When we were younger evrything that happened was so shiny and new and thus soooo much was going on. Now that we know the deal, interesting things, that register only happen every now and then. I mean just look at a baby: It can amazed, hurt, angry and break out in the brightest laugh just because of a wooden cube.
And then there is prolly the fact that the older we grow, the slower we get at things that require conscious intervention – while until a certain age, we get faster at automatic things because they become habits. But then again it is no wonder that a soccer player's career ends around 30, because speed just peeks in our twenties.
Uhh what I just wrote sounds sooo depressing :disappointed_relieved:. But luckily right now it does not really bother me at all, things are just as they are :grin: