Note taking apps are a prime example of this, using a proprietary localdb for notes, inside of app storage you can't access, forcing you to transact with your own data exclusively through the app (and whatever subscriptions or upcharges that come with it). We've trained out the idea that these could just be local text files in a directory you can access and do with what you want.
I've watched discussions around open file formats fade away into obscurity along with the rise of mobile, and now we have to fight on whether we should be so graciously allowed to install software on the devices we own or not.
Not everyone needs to be a computer science student, but some basic level of curiosity or education around how tech works should be required in school, at the very least a warning message of "Your data isn't safe if it's not under your control."
But have you considered that a meaningful number of users actually want functionality that plain text simply can’t provide?
I understand files and file systems, I’ve worked in IT for decades, mostly in open source. I still choose a non plaintext note solution because it delivers capabilities that plain text cannot, especially across devices.
As long as the data can be exported to open formats, why would I voluntarily limit the value and functionality my tools can provide?
That's exactly the point!
The file system is hidden from modern users. Kids brought up on this now have no idea or concept of where their data resides.
It's just not commonly used for the reason the other person mentioned (share buttons between apps that are file type aware)