You eventually restated my point. It's a convention used among a portion of the population, documented in articles and studies, but not taught or a part of formal grammar.
At some point a set of fairly strict rules is important for a written language, as your point with Gen X and Boomers helps to illustrate, because it makes sure you can be understood by a broader audience when clarity is required. Punctuation is a fundamental part of that.
Omitting periods in text is a technilogical colloquialism. I'm not arguing that. But that doesn't mean, as the poster that I first replied to implied, that people who omit periods from texts are the only ones who "know how to write".
Over-use of exclamation points is another poor habit, since they can mark something that's important regardless of it being a positive or negative. With quoted speech it could be something that's either angry or joyful. Using them to convey a non-threatening tone shouldn't be required. I get that it is in some cases, and I belive that indicates a problem with our overall literacy and a renewed misogyny in the workplace.
Whether this is a result of the medium of communication or a decline in literacy is up for debate, but word choice and context should do the bulk of conveying tone and relying on punctuation for that purpose understandably looks like an indicator of poor literacy.