It's hidden on purpose, if you search you'll find posts with broken extensions by not getting the deps too.
 ??
imo, it seems a better to give a link to the ftp* AND have some text saying something like
 "* to use please understand, if  
an_extension.tcz.dep file exist it contains a list of other .tcz extensions that 
an_extension.tcz depends upon to work! "
or more simply put 
       better to inform users of core  , rather than hide info  links  ect