.txt isn't a format - what size will the bytes/words be, what character encoding will they use (EBCDIC? ANSI? ASCII? Fixed width UTF-32?, variable width UTF8?, Next decade's AI-designed super-efficient encoding?) and what human language will they be encoding? Aramaic? Medieval French? As he said we keep using "standard formats" but the standards keep changing, and so does the world around it.

.txt doesn't address the content - something like tables of rainfall needs structure inside the text rather than runs of words. CSV? XML? Markdown or HTML tables? Audio, image, video, or more intricate things like a 3D model of a building?

And it doesn't address the hardware (that PDP tape drive), who has a laptop with an floppy, Iomega Zip, CD or DVD or Blu-Ray drive at all these days? What are you going to do with grandad's SSD with built-in encryption?

That still leaves unanswered questions:

What encoding - ASCII or Unicode? UTF-8, or UTF-16?

What type of filesystem - FAT32, exFAT, ext4?

What physical medium - HDD or SSD?

OP's question goes deeper than just the file format.