An unfortunate side effect of Doctor Who's age and premise is that a staggering amount of characters and storylines have been dropped throughout its run.
The show has been on the air for well over fifty years and has played host to dozens and dozens of writers and directors in that time, with each of these creative minds bringing some fresh ideas and concepts to the table. Unfortunately, not everything is solid gold, and the majority of these don't become mainstays.
Plus, when you factor in the standalone nature of most episodes - as well as the fact that time travel can easily overwrite and change certain things - it's pretty much inevitable that some stories will just become lost within the show's vast history.
While some of these plot points may have been revisited in comics, novels and audio dramas, the fact that Doctor Who doesn't have a clearly-defined canon means that only the core show can be considered the true, actual version of events.
Bearing that in mind then, these storylines were never picked up again after we last saw them, and frustratingly, it's highly likely that things will stay that way for good.