Printable version had one main purpose: Support browsers that didn't support media queries yet.
That purpose is no longer relevant, as the last browser (IE 5.5/6.0) that required it, is no longer supported.
A 3rd use has been to check how a page will look in print. Many browser's web inspectors have a mode to do this, and for the general public, most operating systems provide a "print preview" feature.
As the printable version feature is not well maintained, has a few quirks and adds complexity that is avoidable, I suggest we start fully removing support for printable version.
- Deprecate printableversion (per 1.35)
QA Results - Beta
Removal continues in T259141: Remove printableversion mode