A "Showerthought" is a simple term used to describe the thoughts that pop into your head while you're doing everyday things like taking a shower, driving, or just daydreaming. A showerthought should offer a unique perspective on an ordinary part of life.
I think it's a lot more because the internet was a niche. It's something your parents/family or weird creepy uncle wasn't on. All these old memes still feel "untouched" by facebook and it feels like an in-joke. In other words memes felt more special.
4chan was onto something, once memes became mainstream they died... a little hyperbolic but they do lose their fun factor being more popular now.
And back when 9gag was the main hub for memes and funny content
They annoy the hell out of me because people aren't even trying anymore to make them funny. Yesterday it felt like half of the memes were self-referential "haha it's so funny how we now post the old memes again" shit and people up voted them to the moon.