Like almost every fanfic I've read the characters are all super serious XD
Like, chill dude.
There is no sarcasm in most fanfics.
Everyone's just super stiff and sarcasm is only used by tsunderes.
Which are rare.

I mean like, everyone is totally all stiff neck in rl.
Sarcasm? Pssshhhhh what's that? Some kind of extinct animal?