How come my ibooks on the iphone and ipad are not synchying

Because you haven't set up syncing of iBooks in iTunes?

See this Apple doc -> iBooks: Viewing, syncing, saving, and printing PDFs on iPhone, iPad, and iPod touch

1. Select your iPhone, iPad, or iPod touch in the Devices list on the left in iTunes 10.1 or later.
2. Click the Books tab in the resulting window.
3. Ensure that the Sync Books checkbox is enabled.
4. If iTunes is set to only sync selected books, be sure to enable the checkbox next to the PDF you want to sync.
5. Click Sync.

Why does it not work like photo streaming? Why the need for a computer to sync to using iTunes?

TThanks. Very helpful, I think.