None of the answers satisfy me, though Logan R. Kearsley’s is by far the closest to satisfying me.
EDIT: Uri Granta’s answer satisfies me more than mine. Go read that.
There is a colloquial register in English, in which the first person subject is omitted routinely. It predates social media; see, for example the Beatles’ A Day in the Life. The bits Lennon wrote use the pronoun; the middle section McCartney wrote skips it:
Woke up, fell out of bed,
Dragged a comb across my head
Found my way downstairs and drank a cup,
And looking up I noticed I was late.
Found my coat and grabbed my hat
Made the bus in seconds flat
Found my way upstairs and had a smoke,
Somebody spoke and I went into a dream
But contra Logan, I don’t think this is just spoken English. I think this is a particular narrative register of spoken English—it’s a conventionalised way of telling stories, in a punchy way. I don’t think you’ll find it in different kinds of speech, such as say persuasive speech or instructional speech.