I’ve only seen this expressed in single statement messages, rarely emails or more complex message communication. Periods tend to only be useful for separating standalone statements with sentence complexity, so people may not use them when there is just one statement containing a small word count.

In fact, this is a grammatically consistent behaviour in formal English. As an example, the proper use of a period in bullet points is that they are not used unless the bullet point contained other punctuation marks earlier which increase their reading complexity to a more formal sentence rather than a quick statement. When we message people, we are often just speaking in an exchange of single bullet points due to the inefficiencies of soft keyboards.

If we go into further detail, periods come into play—though, some times we just switch to voice for a more robust and regular style of communication. Similarly, when we use physical keyboards, the speed and ease of them tends to have our spoken complexity go up and subsequently so does the requirement for periods to be used, and they are.

Placing other statement stoppers that are not periods are simply voluntary markers to underscore sentiment of that statement. They honestly have more place in such context as they’re providing actual purpose without the need to expand into multiple sentences or explanation on the slow soft key medium. In that sense, it is also not too dissimilar to and old timer complaining about telegrams using broken English.