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