Originally Posted by Aenaryn:
“No it's not a cop-out, it's the answer to all these "why didn't he just get in the TARDIS and do X to avoid plot element Y". It's being consistent with the rules established in that universe. Ignoring them for David Tennant looking sadly at the Mme would be a cop-out.”
Of course its a cop out. Writers can break any rules they want (witness RTD's continual breaking of said "writers' rules" with him bringing back Rose time and time again with some convenient way of doing it.
It is obvious that Reinette's story was deliberately ignored so as not to detract from that of Rose - even though the Doc fell in love with Reinette and was shown to choose her over Rose.
If they had wanted to bring in Reinette or even have the Doc talk to her grandaughter, they could have.
But that particular story (possible one of the top 3 or 4 episodes since 2005, and one of the Doctor's most emotional moments) was deliberately marginalised and forgotten about.