Sarmat, I'm not sure if you honestly believe what you are saying, have little/no experience with ebooks, or are just yanking our chain???
I regularly use a heading tag for the "block groups" you are talking about
:
Code:
h3 {font-weight:bold; text-align:center; font-size:1.3em; font-family:serif}
h3 img {display:block; margin:1em auto; width:50%; max-width:600px}
h3 span {display:block; font-variant:small-caps; font-size:1.1em}
<h3 title="1 - Having a Little Fun">Chapter 1
<img alt="Gryffindor Crest" src="../Images/ChHd.png"/>
<span>Having a Little Fun</span></h3>
That gives a title for the auto generated-ToC, a "Chapter #" on the first line, an image for a chapter header on the second line, and a chapter name/subtitle on the third line.
It allows proper hierarchy for the different sections of the book:
Code:
<h1> - Cover/Title
<h2> - Part, Section, or Book name
<h3> - Chapter, Appendix, or glossary
<h4> - Subchapter, Appendix/Glossary sections, etc.
It also follows accessibility guidance...
For you to say that heading tags are not used, or are useless, is simply incorrect (hogwash). You may say that YOU don't use them but that is about all...