The Emacs manual says
• The AUCTeX package provides more advanced features for editing TeX
and its related formats, including the ability to preview TeX
equations within Emacs buffers. Unlike BibTeX mode and the RefTeX
package, AUCTeX is not distributed with Emacs by default. It can
be downloaded via the Package Menu (*note Packages::); once
installed, see *note The AUCTeX Manual: (auctex)Top.
Distribution question:
Is there a reason why it would not be possible to bundle the latest
available version of AUCTeX with Emacs, say from ELPA?
