Getting rid of the Doctor-lite episodes is one of the few good things Moffat actually did, why, just why. Why do they bother with them?
Because it saves time and money if you can shoot two episodes simultaneously, one focusing on the Doctor and the other with very little of the Doctor.
Space: 1999 also did this frequently in its second season, alternating between episodes that focused on Martin Landau and had very little of Barbara Bain and episodes that focused on Bain with very little of Landau, so that they could shoot two episodes at a time and avoid falling behind schedule. And that was for most of the season, not just one pair of episodes. (Then there was
Maverick back in the '50s -- initially it had only one lead, but after a few weeks they gave him a brother and alternated between the two leads on consecutive weeks so they could overlap productions and stay on schedule.)
And consider this: The alternative way to avoid falling behind schedule is to do a clip show, an episode consisting mostly of flashbacks to previous episodes. Given the choice, I'd rather see the occasional Doctor-light episode. (I don't think
Doctor Who has ever done a clip show, unless you count the way the ending of "The Wheel in Space" set up a rerun of "The Evil of the Daleks" as a mental projection the Doctor was showing Zoe. "The Trial of a Time Lord" doesn't count, since the "flashbacks" -- and flashforwards -- were new material.)