Being a mechanical engineer student myself, I can see where you're coming from, however, I have to respectfully disagree.

It's true, most professionals use off-the-shelf solutions, the Office/Adobe suite, or other proprietary software like Catia, Autodesk, the likes. I have been nothing but frustrated by these options. I have dealt with gigabyte Illustrator files, as the inexperienced user accidentally embeds all linked media. I have been increasingly frustrated with "made up marketting terms" when saving Adobe proprietary formats, or OneNote's "invisible formatting language". I make a new line, then remove it, and whoops, the whole paragraph has been reformatted, all the equations are no longer in italics (despite this, I still use it for all of my study material, it's fantastic)! It helps to have a Markdown-like mental model when dealing with word processors, you understand the data hierarchy, which is at the end of the day underneath all of that GUI, most people I know who use Word make an absolute mess of the document because they have no idea how to have a consisent layout, they add new-lines, paragraphs, tables, fonts and indententations all over the place and then get frustrated when they don't get the desired results.

While Markdown may not be the best format with the most features, it has a fantastically consistent layout and it's easy to understand the hierachy of information. There is no obligation to use the terminal, you can open it in any visual editor. Also, I would not call the fact that it's plain text instead of XML/binary a limitation but rather a feature, not a "remenant of the 1970s".

There is something amazingly refreshing about knowing that what you see is what you get, I can't stress this enough. Instead of using buggy program that manipulates a mess of an XML file, you describe the layout from scratch and that gets "compiled" to a PDF. This is why programmer source code is written as text, and not in Word, for example, it's just plain information that any compiler can work with to achieve any sort of complexity. There is no hidden document metadata, there is no hidden bloat from [insert proprietary software here] having upgraded the document format several times over the years until it eventually corrupts something (I'm looking at you Premiere Pro, every major version requires you to upgrade your saved project, making a new copy "just in case", it's impossible to go back, and I've had it break several times). It's a single source of truth that describes a behaviour, and the compiler can get better over the years and generate better and better executables from that same code as it improves.

This is the worst argument ever, but it's still an important one: it's free, and works on any OS. There are definitely advantages to using off-the-shelf software, I myself am a heavy user, but I cringe every time I have to work on a messy document with other students, recently I had to work with another student that has macOS and could not get Word to open the document and display equations without converting them to images...

I find the Markdown/Word comparison similar to my experience with Docker and Windows, for those that are familiar with it. Windows, macOS and Linux (although Windows is the worst offender) get bogged down with bloat over time, dnagling files, layers of abstraction, derived from complexity. How many times I wish I could start from a base image, and add/remove (software) features as I go, like building a new Docker image, without losing data.

You bring up scientists, granted, not everyone uses it, but I believe LaTeX is more comparble to Markdown than to Word. It has a text-based source format that gets transformed and rendered as a PDF, but it's way, way too complex for the majority of use cases. If there's a better alternative to Markdown, I'd be glad to try it out, but for now it's my main choice for the long-term storage of information.