Some websites now contain 'responsive images'. These scale (or crop) depending upon your screen's viewing area, so the image sizes remain appropriate whether you're looking at the website on a mobile phone, or on a huge flat screen monitor.
This is an example of responsive text.
The amount of textual detail scales relative to your screen size.
The big problem with many tools used for writing (ok, mostly word processors) is that there are too many things you could be doing instead of writing. You could be playing with fonts or styles, futzing for ages trying to make the document look right, work the number styles, headers and footers and resizing the margining.
Or you could be writing.
With Markdown, the font, style, margin and other stuff all comes later. All you have is the text, the basic structure and the options for bold, italic, lists and tables. That’s it! There’s nothing else, so the writer is encouraged to write.