No one wants to invest time and energy learning a technology they won’t use, but Pressbooks offers a pretty good return on investment.
It’s very easy to learn; if you’ve ever used WordPress, you will likely be very comfortable with the interface. Even if you haven’t, the WYSIWYG input is intuitive, and you can probably pick up the basics you will need to start creating content very quickly.
The versatility of Pressbooks makes it worth learning. Manuscripts of any length can be quickly imported (and short works can be composed directly) in Pressbooks, and then published in a variety of file formats. Authors can easily share links to their web books or post or house EPUB files for others to download and read on various devices.
Arguably the most compelling reason to try Pressbooks is that it’s free. Other than the time invested, nothing is lost if you try your hand at creating and publishing a book.