Why don't my e-books play video?

I read books on screen. It is convenient, simple and cheap.
But why are e-books not designed?
If I buy a book in a bookshop, it will have a particular typeface and chapter headings.
If there are pictures, they will appear at the relevant point in the narrative and they will probably fill a page.
If I read the same book on my Kindle, the typeface is in one of the Kindle’s standard typefaces, as are the chapter headings. And the pictures, if they appear at all, will appear as tiny images, sometimes all together the end of the book.
Why don’t publishers take advantage of the new medium and use video instead of the static pictures in a physical book? Why no sounds files in my Leiber and Stoller biography?
Why is the index not displayed as clickable links to take me to the relevant page?
Is it that publishers see e-books as an annoyance, something cheap and tawdry which is eating into their traditional business?
They would do better to see them as an opportunity.
If video and sound would make a book too large to download in a reasonable time, why not store the video and sound files in a cloud and give people who buy the book at the publisher’s price, or with the publisher’s app, access to them.
I want to hear Riot in cell block #9 when I read my Leiber and Stoller autobiography.
I want to see Bobby Charlton scoring when I read The footballer who could fly.
I want to see Eddy Merckx flying up mountains when I read Half man half bike.
Come on publishers, bring books up to date.