Arabic didn’t have punctuation marks until the 19th century, when a philologist named Ahmad Zaki Pasha developed the punctuation system as part of the modernization process of Arabic. Officially, there is a standardized way to use punctuation marks in Arabic, but in practice this hasn’t really stuck, and you’ll see people using punctuations differently. For example, some people use parentheses (rounded brackets, like these) for quotations and when referring to words, the way quotation marks are used in English, but others use quotation marks. Additionally, “run-on sentences” seem more acceptable in Arabic.
What’s interesting is that even before I learned that punctuation marks are a modern development in Arabic, I thought that Arabic doesn’t need punctuation marks the way English does. I tend to use a more open style (i.e. less periods and commas) in Arabic than I do in English.
The Quran is the most easily accessible example of what Arabic used to be like before punctuation marks. The chapters are divided into verses, but the verse marks don’t always coincide with where a period would go. There are some very long verses that have many sentences.
If it's not for plain sloppiness or laziness, then it might also be that the person is using a 'voice to text' app which often does not care about punctuation.
Oh, punctuation does matter in many cases. In Russian, we often refer to a phrase (saying) "Казнить нельзя помиловать" which lacks a comma. Depending on where you place it, the phrase will convey just the opposite meaning. One is going to be either executed, if you say "Казнить, нельзя помиловать", or pardoned, if you say "Казнить нельзя, помиловать".
Oh, I just looked it up on the web, there are equivalents (and different examples) in other languages. "Pardon impossible. To be sent to Siberia" - the full stop was probably misplaced here. It would've meant the opposite thing, had it read, "Pardon. Impossible to be sent to Siberia".
«Perdón(,) imposible(,) que cumpla su condena» (I don't speak French, just citing an example).
Those eager to learn more about the amphiboly, can read this: https://en.wikipedia.org/wiki/Syntactic_ambiguity .
Thanks a lot for the interesting comments. So, it seems that punctuation is a rather new invention.
Tangentially, if you're interested in this sort of thing you might enjoy a book called Shady Characters: The Secret Life of Punctuation, Symbols, and Other Typographical Marks, by Keith Houston. It's not about punctuation and its function in grammar, it's about punctuation marks and their history in typography. So it's where you find out that the name of this mark ¶ is "a pilcrow," and the surprisingly complicated history of punctuation marks coming and going.
In any case, if I recall correctly, even the space had to be invented. Originally letters were simply written in sequence without word breaks (and alternating left-to-right and right-to-left in successive lines).