Up to recently that was not an option even on the LiveCD.
The boot options on the LiveUSB were, until the latest release, were not selectable by the user.
The next release should have more options added for the user to choose when creating the LiveUSB. The install option should be one of them, if it tests out OK.
Simply adding the word install
to the end of the boot line should do what you need, but this has not been tested.
Else edit the menu.lst file on the USB device ..... copy the standard boot stanza and paste it as an extra boot option, adding the word install and change the 'title' to reflect that it is the "install" option should be a more permanent solution.
I am interested in hearing of feedback to this, so if you do it please let us know how it behaves, thank you.
are we expected to add it manually? if yes, why?
Yes, for the present.
Because no one requested its inclusion before