They're trying to save time it would take on hitting enter and space bars and whatnot.
Your guess is as good as mine.
Though every person might have their own reason.

I'm lazy

Most people can barely manage to write a correct sentence these days, let alone a paragraph. It requires more thought and effort than they are willing to undertake.

I literally just skip over it when I see
one single big block of text, not worth my
time reading it

I think I try to have paragraphs when it’s a long post or reply.

Because many people are used to writing in txt spk which is undoubtedly convenient for them and also shows a degree of constant language evolution, I guess.
However, if the idea of that is to save time messaging, they are hardly then going to complicate things by adding paragraphs or any grammar or syntax which they would see as 'unneccessary' time wasting.
Sad, but inevitable...

Must have missed the memo on this. 🤔

@Sarupticious So what do you think of Tyler Hoechlin and would you do him

I use paragraphs when I have to, but here I write as I think, which is rarely organized enough for paragraphs.

They lives their lives on their phones and it is difficult to write a long sentence much less a paragraph.

@Saraupticious So What Do You Think Of Jason Statham & Would You Do Him

I do.