Why Views Slideshow JCarousel plugin isn't available on view format settings?
There is nothing wrong. jQuery Cycle is the default library used by the Views Slideshow Cycle module. 

Look instead at "Widgets" on the format settings screen. The relevant configuration options will appear by selecting "Pager" under either Top Widgets or Bottom widgets. 

From the Views Slideshow JCarousel project page:


  Currently provides a JCarousel pager widget.


and 


  Under the Format heading, click "format" and select "slideshow". You
  should now be able to select and configure your jcarousel slideshow.
  Pager options are on this configuration screen, not under views "pager
  settings". To decide where you want your pager to go, you can tick the
  pager widget checkbox beneath the area you wish to show it. your
  choices are "top" or "bottom" of carousel.


Note: If using Views Slideshow Cycle, you will need to download the jQuery Cycle plugin.