RP Grammatical question :)

[Arthuro]

Hi people!

So, English is not my first language and I'm wondering why everyone uses the third person while "text role playing" (public chat or bedroom)... *comes behind her/you and pinches her/your buttocks*, *he unzips his fly and lets his pants drop*, *grabs handcuffs...* etc... you know what I'm talking about

Seeing this everywhere I quickly adapted and now use this form myself... but I still don't understand it and to me it feels strange (I would have used the first singular person myself...)

So, as a non native speaker and a curious person by nature, can anyone enlighten me and help me understand?

Does it have some sort of literary roots that i'm not aware of?
Is this some grammatical form that just seems obvious to you because you've been using it since you were kids?
Is it just something that appeared on the internet without anyone knowing the source of it?
Is this for a completely different reason that I'm not seeing at all right now?

Thanks in advance
Keep having fun!