In my experience, younger people who grew up with the internet write their texts and emails as if they are instant messaging, because they grew up with AOL and MSN messenger etc when it comes to text based communication.

Older people who communicated over text before the internet only did this in one way - writing letters.

As a result their style of texting or emailing is often very long form in comparison.

When writing letters you are limited by how much room there is on a piece of paper.

This leads to using some shorthand which used to be fairly common, but has fallen out of public knowledge for younger people.

You could argue that some of the stuff that younger people email or text informally can be just as cryptic because there is entirely different shorthand that millenials and generations Y and Z use.

If you closely examine how you casually communicate with your peers of a similar age, you will notice it can be just as odd as what you experience from communicating with generations on either side of you.